Inglise keel unit 5 answers (0)

1. (a) (i) gene
length of DNA;
codes for a ( specific ), polypeptide / protein / RNA; max 1
allele
alternative form of a gene;
found at a, locus / particular position on, a chromosome; max 1
(ii) assume allele refers to coat colour allele
(coat colour) gene / alleles, only on X chromosome;
A no (coat colour), gene / allele, on Y chromosome
male cats , XY / only have one X chromosome;
males have only one (coat colour) allele / cannot have two (coat colour)
alleles;
need black and orange alleles for tortoiseshell colour; 2
(b) parental genotypes CrCr × CwCw;
gametes Cr, Cw;
F1 genotypes and phenotypes 1 mark:
F1 genotypes (all) CrCw
F1 phenotypes (all) pink ;
F2 genotypes and phenotypes 1 mark:
gametes Cr, CwCr, Cw;
F2 genotypes CrCr CrCw CrCw CwCw
F2 phenotypes red pink (pink) white;
F2 ratio 1:2:1;
accept other symbols if key given .
accept r and w as symbols without key. 6
(c) (i) 65; 130; 65; 3
(ii) 0.138 + 0.007 + 0.061; (or other suitable working )
0.206 – 0.208;
2 marks for correct value if no working shown
ecf for both marks but calculated value must be to three decimal
places 2
(iii) support , figure lower than 5.991 / figure lower than critical value;
R ‘support’ on its own.
ecf applies if value in (ii) is incorrect 1
[16]
2. named characteristic ;
named environmental factor ; (mark first answer only) 2
[2]
3. 1 ref to operon;
2 normally repressor substance bound to operator ;
3 prevents RNA polymerase binding (at promoter) / prevents
transcription;
4 lactose binds to repressor;
5 changes shape of protein molecule;
6 unable to bind (to operator);
7 RNA polymerase binds (at promoter) / transcription occurs / genes
switched on;
8 AVP; e.g. production of lactose permease / production of beta -
galactosidase; max 5
[5]
4. a change in the genetic material ;
unpredictable / AW;
extra detail; e.g. addition / substitution / deletion / frame shift / small
part of chromosome / may code for different protein /
may code for no protein
[2]
5. 1 mark max for general effect of mutations:
mutation may give different, amino acid / primary structure;
A ref stop codon
some mutations alter , molecular shape / tertiary structure / binding;
max 3 for explaining data in Table:
so unable to, accept / transport, HCO3 -;
unable to bind ATP;
so increase in acidity / decrease in pH;
effect on mucus;
effect on enzyme (s) /ref pH optimum of enzyme(s);
poor digestion of, protein / lipid / starch;
AVP; e.g. some mutations, give some transport / have less effect.
> 33% (of norm) allows normal digestive function / [A very low] does not. max 3
[3]
6. (a) (i) award both marks for correct answer
10 000 / 800 000 (× 100);
1.25 / 1.3 / 1(%); 2
(ii) R any reference to energy / light missing the plant
reflected (off plant) / only certain wavelengths of light can be, absorbed /
used; ora
absorbed by / hits, non-photosynthetic parts; e.g. bark
passes through leaf / misses chlorophyll / misses chloroplasts;
some is heat that is used in evaporation / respiration; max 2
(iii) bacteria / named bacterium decomposer; (Nitrobacter, Nitrosomonas) 1
(iv) take the first 2 answers:
death / dead remains;
excretion; R waste products
egestion;
other suitable method ; e.g. insects moulting
hatched eggs
moulting (fur / feathers )
R leaves 2
(b) Primary consumers are eating and…
producers have, cell walls / cellulose; ora
difficult to digest / much material, wasted / egested;
energy used by gut microorganisms ; ora
much material cannot be eaten (by primary consumer ); ora 3
[10]
7. (i) plasmid cut by restriction enzyme;
at specific sequence;
same enzyme as used to cut (insulin) gene;
sticky ends / described ;
ref. complementary sticky ends;
ligase seals ( sugar - phosphate ) backbone / AW; max 4
(ii) credit any two from the following :
1 antibiotic resistance (gene) introduced and survivors have plasmid;
2 fluorescent marker (gene) introduced and glowing bacteria have plasmid;
3 identify bacteria producing insulin using antibodies; 2
[6]
8. referring to pig insulin:
ethical / religious , reasons;
incompatibility / lack of tolerance / immune response; ora
not exactly the same as / less effective than, human insulin; ora
referring to human insulin from bacteria:
engineered insulin is cheaper ; ora
greater supply of engineered insulin; ora 1
[1]
9. allow max 5 for following:
transcription;
DNA unzips / H bonds break;
exposing required , gene / sequence of bases ;
RNA nucleotides align with DNA;
U with A, A with T, C with G, and G with C;
RNA polymerase;
mRNA formed (using DNA strand as template );
leaves nucleus through pore;
allow max 5 for following:
translation ;
mRNA attaches to ribosome;
tRNA brings amino acid (to, ribosome / mRNA);
each tRNA attached to specific amino acid;
tRNA binds to mRNA using complementary, base triplet / anticodon;
peptide bond formed between amino acids;
DNA / mRNA, (nucleotide / base) sequence determines sequence of
amino acids;
AVP; e.g. 2, base triplets / codons, in ribosome
AVP; e.g. ref. to : start / stop, codons
polysomes
large and small subunit in ribosome
Mg2+
[10]
10. (a) from below / ventral / AW; A idea of brain being seen from below
R upside down, looking upwards 1
(b) (i) reject choice of answers, accept any reasonable spelling
A cerebrum / cerebral hemisphere / cerebral cortex / frontal lobe ;
ignore refs to right or left R incorrect lobe
B pituitary ( gland ); R hypothalamus
C cerebellum;
D medulla (oblongata) 4
(ii) control of breathing;
control of heart rate ;
control of circulation;
control of swallowing / salivation / vomiting reflex; 2
(c) If blood hormone concentration rises
inhibits output of trophic hormones by pituitary gland;
which inhibits output of hormones by endocrine glands;
blood hormone concentration falls to normal levels;
ref. negative feedback;
ORA max 2
[9]
11. (a) (apical / terminal ) bud is source of auxin;
auxin inhibits growth of side shoot / ora;
remove bud and auxin concentration drops;
(this allows) cell division / elongation to take place ;
ecf – marking points 2 and 3 if growth regulator or hormone used
instead of auxin max 3
(b) award two marks if correct answer (80%) is given
award one mark for calculation if answer is not correct
(90 – 50 = 40) 40 / 50 × 100;
80%;; 2
(c) no growth until day, 8 / 10;
auxin moves out of paste / AW;
inhibits growth;
growth occurs after, 8 / 10, days ;
because auxin, levels fall / ‘used up’; 3
[8]
12. (i) max 1 for meaning of term
attached to an insoluble material / AW;
max 2 for description
(micro)encapsulation / (trapped) in alginate beads;
adsorption / stuck onto, collagen / clays / resin / (porous) glass ;
cross linkage / covalent / chemical, bonding to, cellulose / collagen fibres;
gel entrapment / trapped inside gel e.g. silica (lattice / matrix );
partially permeable membrane (polymer) microspheres; 3
(ii) any three from the following:
urine can be processed / no problem of removing urine / AW;
pure / drinkable / useable, water produced; A water recycled
space saving / less water needs to be taken into space;
payload limit / weight reduction / AW;
no problem in separating enzyme from products / product not
contaminated;
ref. to longer shelf -life of enzyme;
no need to take more enzymes into space / enzymes reusable;
A enzymes recoverable
AVP; e.g. larger surface area of enzyme exposed, more stable at
extremes,
ref. to ease of use (of bioreactor) 3
[6]
13. (i) adding / using, water to break, bond / ester bond, (in molecule);
A breakdown into smaller molecules 1
(ii) matrix, protects / stabilises, enzyme / lipase;
functions , at optimal rate / more efficiently , at higher temperature / 45 °C;
A greater activity / AW
ref. to soluble lipase begins to denature (reducing activity); ora
functions, at optimal rate / more efficiently, at lower pH;
ref. to presence of fatty acids changing pH;
ref. to ionic bonds breaking (in soluble lipase); ora
AVP; e.g. ref to industrial uses
ref to effect on R groups max 4
[5]
14. (a) starts with previously uncolonised area / bare ground / bare rock / AW;
ref to pioneer species / named pioneer;
series of recognisable, seres / stages;
progresses to, climax / final equilibrium stage; max 2
(b) stabilise environment;
soil development / increase humus / organic material;
change soil pH;
hold more water;
release more minerals or nutrients / increase N content or fix N / hold
ions;
form microhabitat / reduce exposure / provide shelter / reduce erosion; max 3
(c) any two from following:
grazing;
burning;
mowing / application of fertilizer / application of selective herbicide;
exposure to wind;
grass able to continue to grow ( linked to a statement above ); 2
(d) increases ;
plants at later stages are large / plants in early stages are small;
trees / shrubs . are woody , appear later in succession; 2
[9]
15. max 1 mark from following:
1 economic definition of sustainable ; e.g. similar quantities of timber
can be harvested year on year
2 grants for planting forests / management schemes;
3 planting to ensure sustainable harvest rate;
max 3 marks for planting strategy :
4 trees not planted too closely together;
5 support young trees to prevent damage e.g. from grazing animals ;
6 species planted that are suitable for prevailing conditions /
native spp;
7 softwood sp. / conifers / named conifer / fast growing sp. planted;
8 deciduous broadleaved species around edges for aesthetic reasons;
9 creates different habitats / named habitat / protected habitats/ some
fallen trees left to rot;
max 3 marks for felling/cropping strategy:
10 ref. to clear felling having negative effects e.g. soil erosion;
11 only mature trees removed / selective felling / individual trees;
12 some clearings / rides / glades in woodland / strip felling;
13 control of, pests / diseases / fire prevention ;
14 ref to coppicing / pollarding;
15 (deciduous trees) regrow from base/ idea of rotation / cycle ;
16 standards / large trees not coppiced, as encourages biodiversity; 7
[7]
16. population;
habitat;
community;
ecosystem;
(first) trophic; R tropic
producers/( photo ) autotrophs/autotrophic;
(primary) consumers/heterotrophs/heterotrophic/herbivore;
R carnivore/other qualified consumer 7
[7]
17. 1 mark per correct row
Look for both ticks and crosses.
If a table consists of ticks ONLY or crosses ONLY, then assume that the blank spaces are the other symbol .
If a table consists of ticks, crosses and blanks then the blanks represent no attempt at the answer.
Nucleotides line up along an exposed DNA strand. ;
The whole of the double helix ‘unzips’. ;
Uracil pairs with adenine. ;
A tRNA triplet pairs with an exposed codon. ;
Both DNA polynucleotide chains act as templates. ;
Adjacent nucleotides bond, forming a sugar-phosphate backbone. ;
The original DNA molecule is unchanged after the process . ;
Adenine pairs with thymine. ;
[8]
18. (a) (clinically) obese/ obesity ; R morbidly obese 1
(b) Diet B
essential fatty acids/linoleic acid/linolenic acid/fat soluble
vitamins/A/D /E/K;
Diet C
sugars/named sugar/starch; A vitamin C 2
(c) (i) B;
energy intake (of B) is lower ORA; 2
(ii) energy intake is less than energy used ORA; 1
(d) (no fruit may mean ) scurvy/described; R vitamin C deficiency unless qualified
raised, cholesterol/LDL, levels in blood; R intake
fatty substances deposited in artery walls/atherosclerosis;
coronary arteries;
narrows lumen;
reduces, blood/ oxygen , delivered to heart muscle ;
CHD/heart attack/angina;
thrombosis/clot;
raised blood pressure /hypertension;
stroke ;
stress on liver ;
stress on kidney;
due to excess protein/amino acids/urea;
AVP;
AVP; e.g. deposition of subcutaneous fat/AW
obesity
stress on joints
anorexia/ bulimia /obsession on diet
constipation
bowel cancer
hypoglycaemia
giddiness
lethargy/ fatigue /tiredness [but R ‘lack of energy’] 3 max
[9]
19. (i) tree cut, close to ground/down to its stump /AW; R down to trunk
new growth forms /AW;
harvest after a number of years /process repeated;
rotational coppicing/AW;
ref to how coppicing increases biodiversity
e.g. increasing light intensity; max 3
(ii) (standards) large planks /AW; A used as timber
A standards more valuable/AW
( coppice ) small diameter wood /fencing/hurdles/ garden
furniture/ charcoal /firewood/matches;
(coppice) continuous , source of timber/income;
recreational use/ nature reserve ; A ref to tourism max 2
[5]
20. release of carbon dioxide;
from fungal respiration;
available for photosynthesis/carbon fixation;
extracellular digestion;
named enzyme(s);
release of, inorganic substance/minerals/named mineral ; R nutrients, nitrogen
A nitrogenous compound
uptake through, roots / root hairs;
named use of mineral in plants;
ref. to humus;
ref. to beneficial role of humus in soil; e.g. increase water retention , improve soil
structure, stabilize soil max 4
[4]
21. (a) (i) sympatric; 1
(ii) ranges of two species, overlap/close together/AW;
no geographical barrier;
ref to behavioural/genetic/physiological/prezygotic barrier;
correct ref to named area of map; max 2
(b) ref to mate selection by size ; ie large with large or small with small
ref to monogamy;
ref to intermediate sizes, at disadvantage/selected against/ora;
intermediate do not pass on alleles/ora;
suggested reason why intermediate at disadvantage/ora max 3
(c) female produces a lot of eggs;
selects male , that can store lots of eggs/has a large pouch/ora;
large males fertilise many eggs/ora;
chance of more offspring surviving;
or
large female and small male produce intermediates/ora;
intermediates at disadvantage/ora; max 2
[8]
22. (i) crossing over; treat chiasma(ta) as neutral 1
(ii) prophase; 1
(iii) have different, alleles/base sequence of DNA;
A sister chromatids have same alleles/non sister have different alleles 1
[3]
23. two different genes represented in each gamete ie Q or q and R or r;
four correct combinations ie Q and R, Q and r, q and R, q and r; 2
[2]
24. (i) (parental genotypes:) AaBb × aabb;
(gametes:) AB, Ab, aB, ab (all) ab;
(offspring genotypes:) AaBb, Aabb, aaBb, aabb;
(offspring phenotypes:) grey body /normal wing, grey body/ bent wing,
black body/normal wing, black body/bent wing;
[sequence of phenotypes must match genotypes for mark]
(phenotypic ratio:) 1 : 1 : 1 : 1;
apply ecf.
accept alternative symbols if a key is given, but if no key given max 4 5
(ii) 80,80,80,80; 1
(iii) (working) 0.1125 + 0.3125 + 0.05 + 0.45;
= 0.925; A 0.9/0.92/0.93
2 marks for correct answer with no working.
ecf if correctly use wrong figures from (ii) 2
(iv) yes (but no mark for yes on own)
as calculated figure is smaller than 7.82;
ecf applies to value calculated in part (iii) 1
[9]
25. (a) (i) due to mutation; A named mutation
has changed, gene/allele/base sequence/DNA;
random ;
irradiation/other named mutagen;
genetically engineered;
altered, mRNA/enzyme/protein;
selective breeding; max 2
(ii) light intensity;
carbon dioxide;
water/humidity;
temperature;
mineral content of soil/potting compost; R nutrients
pH;
lighting regime ; max 2
(b) wild type
no significant/very little , difference ;
those with water taller/ora;
18 day result an anomaly;
ref to figures from table; need two figures at same age with correct
units
dwarf
those with gibberellin taller;
difference greater as they get older;
still shorter than wild type;
ref to figures from table; need two figures at same age with correct
units
only penalise lack of units once
calculation of % difference between treatments for either wild type or
dwarf; max 5
(c) dwarf unable to produce ( active ) GA/ora;
dwarf lacks enzyme for (active) GA formation /ora;
details of why dwarf lacks enzyme; A has, recessive/mutant allele max 2
[11]
26. (i) R questions
embryo, potential human/ member of society/right to life/ killed /AW;
may be from abortion;
scientist making decision for use of embryo/consent may not be required;
parents may not know fate;
religious objection;
may involve cloning ;
some stem cells can be obtained instead from umbilical cord ;
AVP; 1 max
(ii) treat/cure for, anaemia/sickle cell anaemia/named blood disease ;
blood, for transfusion/to replace loss;
treat, immune disorders/SCID/lupus;
treat, non-Hodgkins lymphoma/some types of cancer/leukaemia;
treat/cure for, Alzheimer ’s disease;
treat/cure for, Parkinson ’s disease;
treat paraplegics/ repair injury to, nerves/ spinal cord;
treat, genetic disorders affecting nerves/ Huntington ’s/Tay Sachs /Lou
Gehrig’s;
treat multiple sclerosis/ motor neurone disease;
AVP; eg. stroke/brain damage/retinal repair
AVP; must be relevant to use of blood cells or neurones 2 max
[3]
27. (i) indicates the range of results ;
on either side of the mean;
indicates, variability/(standard) deviation /(standard) error ;
indicates if data sets significantly different; 2 max
(ii) no/small, increase/figs. quoted;
lag phase;
adjust to conditions/detail of adjustment;
produce enzymes;
AVP; 2 max
(iii) more rapid growth in non-deficient cells/ora;
figures in support from both axes of graph ;
low ribose in G6PD deficient cells/ora;
less available to, parasites/ Plasmodium ;
less production of RNA/ribonucleotides;
less available for transcription;
inhibited protein synthesis ;
less protein available for, reproduction/growth/cell division; 4 max
[8]
28. deficiency gives resistance to malaria ;
deficient/resistant, individuals more likely to survive ;
alleles, passed to next generation;
natural selection;
presence of Plasmodium is selection pressure;
frequency of this allele increases;
phenotype more common in population;
AVP; e.g. others more likely to die of malaria 3 max
[3]
29. (a) ( dominant ) epistasis; 1
(b) ref. frame shift;
ref. three extra, triplets/amino acids;
may introduce stop code so shorter, polypeptide/protein;
may increase length of, polypeptide/protein;
may alter, shape/3’ structure, of, polypeptide/protein;
affects active site;
protein/polypeptide, may lose function;
protein/polypeptide, may have different function; max 4
(c) (i) Parental phenotypes: White Leghorn x Red Junglefowl
Parental genotypes: IICC x iiCC or IIcc x iiCC;
F1 genotype: IiCC or IiCc; 2
(ii) 3 white : 1 pigmented or 13 white : 3 pigmented; 1
[8]
30. gene bank;
source of alleles;
for future (selective) breeding;
to counteract, genetic erosion/loss of genetic variation ;
to counteract, inbreeding/homozygosity;
to counteract extinction ;
for changed conditions;
example of changed conditions; e.g. climate/environment/disease/ fashion
to preserve as yet unidentified, alleles/ traits ; max 4
[4]
31. pigmented birds more likely to be damaged;
at all percentages;
more damage as percentage of pigmented birds increases to 23%;
more damage as percentage of white birds increases to 24%;
fall in damage of white birds at, 25%/ highest percentage; max 3
[3]
32. (i) for benefit of humans ;
to improve, trait (s)/named trait;
to produce desirable, phenotype/genotype;
to increase number of desirable alleles;
to increase homozygosity;
AVP; max 2
(ii) ref. self-pollination;
ref. inbreeding;
limited gene pool; max 2
(iii) ref. different numbers of chromosomes;
hybrid is 3n;
sterile;
gametes have 22 and 11 chromosomes/hybrid has 33 chromosomes;
some chromosomes unpaired;
failure of meiosis;
ref. uneven distribution of chromosomes;
ref. other barrier to interspecific cross; max 2
[6]
33. meristematic/pluripotent/totipotent/cambial/undifferentiated, tissue;
sterile conditions;
nutrient medium to encourage , division/mitosis;
produces callus;
subdivided;
different (nutrient) medium to encourage differentiation;
detail of either medium; e.g. named nutrient or plant growth substance
grows to plantlet;
hardening medium/sterile soil; max 5
[5]
34. stated advantage ;
detail; e.g. particular character (not whole phenotype)/can alter one trait
only (without affecting background genes)/can add allele from
different taxon with which breeding may not be possible/quicker
(than the many generations of, selective breeding/backcrossing) 2
stated disadvantage;
detail; e.g. cannot precisely position insert (so) unknown/unanticipated
effect/may pass to other species (with unknown/undesirable,
effect)/regarded as ethically undesirable (no market /crop
destroyed by protesters)/cannot breed from GM ( requires cloning) 2
[4]
35. (i) ;
(tick);
; 4
(ii) discontinuous ; [do not allow if no reason given] 1
reason
one, gene/locus; A major /Mendelian, gene
discrete phenotypes/ora;
qualitative /large effect/little environmental effect; max 1
[6]
36. (i) endonuclease;
cuts DNA;
with sticky or blunt ends;
at, palindromic/AW/specific/4 to 6 base pair /restriction, site;
from bacteria;
for cutting ‘phage DNA; max 3
(ii) 2 sources DNA;
ref. sticky ends;
complementary binding;
H-bonds between bases;
A to T and C to G;
nicks in sugar-phosphate backbone sealed/AW;
by ligase; max 4
[7]
37. (a) (i) two recessive alleles/homozygous recessive/two of allele 2;
no, normal dominant/allele 1;
homozygous same allele as affected child ; 2
(ii) deletion removes base pairs;
shorter/lighter, pieces of DNA move further in electrophoresis;
towards anode;
so allele 2, shorter/lighter, than allele 1; max 3
(b) 0.25/25%/1 in 4; 1
[6]
38. ref to, leaching/runoff, into waterways;
causing algal blooms;
blocking of light for aquatic plants;
ref to, decomposition/high numbers of decomposers ;
leading to high BOD;
reference to ‘ blue -baby’ syndrome ;
links to haemoglobin; max 4
[4]
39. 1 ref to setting grid /area to be sampled;
2 suitable systematic method chosen/ref to belt /line transect;
3 ref to repetition of line transects;
4 use of quadrats;
5 use of appropriate sized quadrat;
6 details of regular quadrat placing;
7 identify species/use of keys;
8 presence or absence in quadrat;
9 calculation of % of species frequency;
10 measure % cover /use of appropriate scale ; e.g. ( Braun -blanquet/ACFOR/
DAFOR/DOMIN)
11 ref to analysis of data/use of kite diagram ;
12 AVP; ref to relevant statistical analysis, e.g. Spearmans Rank Correlation max 7
QWC - clear well-organised answer using specialist terms 1
[8]
40. routeways/pathways allowing movement of (insects);
ref to connectivity/AW;
ref to sites of refuge/habitat; max 2
[2]
41. pest remains/not totally eradicated;
slow to work /AW;
labour intensive/AW;
reintroduction often needed;
predator may eat crop;
risk of migration ;
risk to other organisms/mutation/predation of other species; max 2
[2]
42. pollination;
maintain biodiversity;
benefits to food chain /food for other organisms; max 2
[2]
43. increased profit for farmers/shops;
no residues on food;
no pesticides;
less use of inorganic fertilizers;
less risk of pollution;
benefits to soils structure and quality ;
benefits to biodiversity;
benefits to human health; max 3
[3]
44. (i) A scapula
B humerus
C ulna
D radius ; 2 or 3 correct = 1 mark, 4 correct = 2 marks 2
(ii) ligament
holds bones together/prevents dislocation;
high tensile strength ;
flexible;
cartilage
ends of bones;
low friction / smooth /slippery;
ref. shock absorber/stops bones rubbing together; 4 max
(iii) biceps / brachialis ;
(contraction) pulls on radius;
flexor (muscle)/bends arm/pulls lower arm up; 2 max
triceps ;
(contraction) pulls on end of ulna;
extensor (muscle)/straightens arm/pulls lower arm down; 2 max 3 max
[9]
45. ( calcium ions/Ca2+) released from sarcoplasmic reticulum ;
bind to troponin;
troponin changes shape;
troponin/tropomyosin, moves;
myosin binding site exposed;
myosin head binds (to actin); 3 max
[3]
46. (Alzheimer’s)
1 reduced uptake of isotope/less positrons emitted/less glucose in brain
2 cells;
3 reduced blood flow;
4 reduced brain activity;
5 reduced respiration in cells;
AVP; e.g. parts of brain accept reverse argument for all points 3 max
[3]
47. (i) control explained/AW; R control without explanationf 1
(ii) mean number of errors reduced in subsequent trials;
in all trials rats with phenserine had fewer errors/ora;
ref. paired data for 2 trials; 2 max
(iii) ref. trial and error;
ref. associative learning ;
ref. operant conditioning;
escape is reward/reinforcer; 3 max
(iv) inhibits acetylcholinesterase;
effect on enzyme;
in synapses;
slows down fall in ACh concentration/keeps some ACh at synapses/slows
breakdown of ACh;
in parts of brain associated with memory ;
improved short term memory; 3 max
[8]
48. innate/instinctive/stereotypic;
inherited/genetic/inborn;
does not require , learning/ conscious thought ;
AVP; e.g. reflex 3 max
searches for breast/bottle/AW; 4 max
[4]
49. (a) plants/protoctists;
animals/fungi/protoctists;
A protoctists once only R taxa that are not kingdoms 2
(b) energy
movement/locomotion/muscle contraction/cilia/flagella;
active transport; A example
anabolic reactions/AW; A e.g. protein synthesis/DNA replication
(movement of chromosomes in) mitosis/meiosis;
nerve impulse/electrochemical gradients;
maintain body temperature/ generate heat;
AVP; (eg bioluminescence/electrical discharge)
AVP; (detail of any point) 3 max
carbon
in, biochemicals/macromolecules; A in organic matter
e.g. carbohydrate/protein/lipid/nucleotide/nucleic acid;
A named examples
growth;
repair;
AVP; e.g. detail of any point) 3 max max 4
(c) (nitrifying bacteria) help/increase, plant growth;
bacteria make nitrate (available);
plants need nitrate;
for, amino acids/protein/chlorophyll/DNA;
for, new cells/mitosis/new leaves; max 2
(d) (i) chemoheterotrophic; 1
(ii) photoautotrophic; 1
(e) (i) carbon; R CO2 1
(ii) Desulfovibrio, uses sulphur (S)/ makes hydrogen sulphide (H2S);
green sulphur bacteria, use H2S/make S;
colourless sulphur bacteria use H2S; max 2
(f) colourless sulphur bacteria; 1
(g) C. perfringens similar to C. difficile/AW;
(bacteria) anaerobic ;
(tissue damage/poor blood supply) decreases oxygen available;
conditions suitable for Clostridium to multiply;
AVP; max 2
[16]
50. (a) (i) U A C C G G A U U C A C;;
1 error = 1, 2 errors = 0
allow 1 mark for giving T throughout instead of U
(i.e. T A C C G G A T T C A C = 1 mark) 2
(ii) transcription / transcribed; R transcriptase 1
(b) (i) J anticodon; R anticodons
K transfer RNA / tRNA;
L ribosome / rRNA;
M codon; R codons 4
(ii) 1 DNA triplet / codon / M / mRNA triplet, codes for
specific amino acid;
2 order of, triplets / bases, determines the order of amino acids;
3 tRNA / K, has, corresponding / complementary,
triplet / anticodon;
4 (tRNA / K) attached to specific amino acid;
5 activation of amino acid;
6 2 (tRNA) binding sites on the ribosome;
7 codon and anticodon bind; A match
8 A to U and C to G;
9 adjacent amino acids join ;
10 peptide bond; 4 max
(c) 1 attaches to ribosome;
2 removes, base / portion, of ribosome;
A stops ribosome assembling / changes shape of ribosome
3 prevents ribosome, attaching to / reading, mRNA;
4 prevents codons being exposed;
5 prevents, tRNA / anticodon, attaching to, mRNA / codon;
6 prevents / inhibits enzyme responsible for, formation of
peptide linkages;
7 AVP; e.g. further detail of any of the above points 2 max
[13]
51. max 7 for the process of genetic engineering
max 2 for the advantages
1 identify / find , gene (for insulin) / length of DNA coding for insulin;
2 obtain / isolate / extract,
gene / length of DNA (for insulin); obtain / isolate / extract,
mRNA (for insulin);
3 restriction enzyme / named e.g.; reverse transcriptase;
4 cut plasmid; cut plasmid;
5 use same restriction enzyme; use restriction enzyme / named e.g.;
6 ref to, complementary ends / sticky ends / described;
7 insert, gene / AW, into plasmid;
8 recombinant DNA;
9 plasmid uptake by bacteria;
10 identify those bacteria that have taken up the plasmid;
11 provide with, raw materials / nutrients;
12 fermenter / bioreactor;
13 bacteria produce insulin;
14 extract and purify / downstream processing ;
15 AVP; e.g.. detail of uptake by bacteria
method of identifying those that took up plasmid
PCR
ligase 7 max
16 advantage 1; e.g. more reliable supply
17 advantage 2; greater / faster, production
overcomes ethical problem described
less risk of disease
less risk of, rejection / side effects
human insulin so more effective 8 max
QWC – clear, well organised using specialist terms;
award QWC mark if four of the following are used 1
gene plasmid
restriction enzyme complementary
named e.g. of a restriction enzyme sticky end
reverse transcriptase recombinant DNA
fermenter / bioreactor
[9]
52. (i) asexual; A binary fission / cloning ignore mitosis 1
(ii) 1 restore diploid number when gametes fuse / AW;
2 prevents doubling of chromosome number
(in each successive generation);
3 without use of gametes there is less variation;
4 no input of genetic material from more than one individual;
5 triploid / 5n / etc, would be infertile;
6 AVP; e.g. polyploid would result in loss of variation 2 max
[3]
53. (a) (i) denitrification; 1
(ii) Rhizobium; 1
(iii) active transport / diffusion ; 1
(iv) nitrification; 1
(b) max 3 for each method
ploughing-in
1 legumes / named e.g., possess, (root) nodules /
nitrogen fixing bacteria;
2 Rhizobium, performs nitrogen fixation / described;
3 nitrogenous compounds are present in, roots / nodules /
legumes / plants;
4 made available to soil if, ploughed in / not removed;
5 roots / AW, decomposed / acted on by decomposers / rot / decay ;
6 nitrogenous compounds released (by decomposers);
7 formation of nitrate; 3 max
crop rotation
8 different, crops / plants, have different (nutrient / nitrate)
requirements ;
9 each year, different demands made on the soil / nutrients not
being removed at the same rate;
10 in, 4th / fallow, year, no (little) nutrients removed / used
for grazing animals;
11 nutrient levels allowed to build up;
12 use legume in rotation;
13 tuber / root, crop to improve soil structure; 3 max
4 max
[8]
54. (i) R if refer to body muscles
less, oxygen / nutrients / sugars / fatty acids, supplied (to heart muscle);
slower removal of carbon dioxide;
less, respiration / ATP made;
muscle contraction is weaker / cannot pump as forcefully /
contraction stops;
death of heart muscle;
makes (remaining) heart muscle work harder / hypertrophy; max 3
(ii) angina / chest pain when, exercising / exertion;
reduced ability to perform exercise;
breathlessness;
myocardial infarction / heart attack / cardiac arrest; max 2
[5]
55. idea of soil development; A ref to depth or fertility of soil
(increase), organic material / humus;
(increase) in availability of water;
minerals available; A nutrients
(some pioneer species) carry out nitrogen fixation;
photosynthesis (fixing carbon);
create habitats / provide shelter;
AVP; e.g. increase weathering, stabilise sand / soil 2 max
[2]
56. (i) final stage in succession / AW;
(community) in equilibrium with environment; 1 max
(ii) eat / trample, seedlings (of shrubs / trees) / AW; R eat grass
prevents, succession / establishment of next sere ; 1 max
[2]
57. (a) award two marks if correct answer (18.4) is given
incorrect answer (or no answer) but correct working = 1 mark
44 / 239 (× 100)
18.4%;;
ecf applied for minor addition errors +/- 2 2
(b) 1 lay, tape / string, across path ; R along the path
2 include trampled and non trampled areas in same transect;
3 use of quadrat;
4 ref to how quadrat is placed; R random
5 count number of plants / percentage cover of plants;
6 plot a graph;
7 repeat the transect;
8 carry out statistical test ( Mann -Whitney / Spearman’s rank);
9 AVP; e.g. detail of sampling technique 5 max
[7]
58. chinchilla – CChCCh CChCH CChCa;
agouti – CACA CACCh CACH CACa; 2
[2]
59. max 3 from points 1 to 5
1 limited, food supply / space;
2 competition ;
3 predation;
4 disease;
5 reached carrying capacity / death rate = birth rate;
marking points 1 – 5 linked to keeping population stable
6 individuals show variation;
7 variation due to, combination of alleles / mutations;
8 best adapted survive / ora; A survival of fittest idea
9 reproduce;
10 pass alleles to offspring;
11 frequency of favourable alleles will, increase / be maintained; A ora 5 max
[5]
60. light / daylength;
gravity;
water / humidity;
touch;
chemicals ; R carbon dioxide
temperature; A heat 3 max
[3]
61. tissue
1 meristematic;
2 undifferentiated / totipotent / able to develop into any cell type /
unspecialised;
3 (cells) can still divide / undergo mitosis;
4 virus free; max 2
sterilising agent
5 aseptic technique;
6 prevent, growth of / contamination by, bacteria / fungi;
7 could overwhelm / grow faster than / compete with, plant tissue;
A AW max 2
cytokinins, auxins
8 plant growth, regulator / promoter / hormone;
9 cytokinins stimulate, shoot / stem, growth / many branches;
10 auxins stimulate growth of, root / root hairs; max 2
magnesium , nitrate ions, sucrose
11 magnesium for, chlorophyll / photosynthesis;
12 nitrate (ions) needed for, protein / enzyme / chlorophyll / named chemical;
13 sucrose converted to, glucose / fructose / monosaccharide;
14 used in, respiration / release energy; max 3
15 AVP; e.g. further detail e.g. cytokinins stimulate cell division
no vascular tissue therefore disease free 6 max
QWC – clear well organised using specialist terms; 1
award QWC mark if three of the following terms are given in correct
context
meristematic
undifferentiated
totipotent
mitosis
aseptic
contamination
regulator
promoter
hormone
chlorophyll
photosynthesis
respiration
[7]
62. (a) linkage
(two or more) genes / loci, on same chromosome; R alleles
do not assort independently (in meiosis) / inherited together;
crossing over
reciprocal exchange of portions of, chromatids / DNA; A swapping alleles
between ( paternal and maternal ) homologous chromosomes; A bivalent
in prophase I (of meiosis); max 2 max 3
(b) anthers removed ( before maturity) (to produce male sterility);
male sterilisation; genetic or, PGS / hormone
pollen transferred by hand ;
plants isolated;
flowers bagged (before and after pollination); max 3
(c) (i) R ‘chance’ alone
chance fertilisation;
chance re picking 50 offspring;
chance re other traits affecting survival;
AVP; e.g. position effect, different gene interactions affecting
expression,
effect of crossing over on numbers of other classes max 1
(ii) award two marks if correct answer (16%) is given without working
recognition of recombinant classes;
× 100;
=16%; max 2
(iii) 1,2 × ;; A (AB)(ab) × (ab)(ab)
3 both chromatids per chromosome shown;
4 crossover shown;
5 result of crossover shown;
6 most / 84%, gametes A B and a b [ × a b]; A AB and ab
7 = parental;
8 few / 16%, gametes A b and a B [ × a b ]; A Ab and aB
9 = recombinant;
10 ref 16 map units apart / close together; max 6
[15]
63. (i) production of desired changes in phenotype of an organism;
selection of appropriate alleles / AW;
by artificial selection;
use as parents / mate, those showing desired phenotype
(to larger degree ); max 2
(ii) measure of value of individual’s genotype (for breeding);
mate with number of proven individuals;
assess phenotypes of offspring; R genotypes
average value;
especially useful for sex-limited traits; R sex-linked
e.g. sex-limited trait; max 4
[6]
64. description
D1 chosen male and female mated;
D2 ref to desired characteristic / named desired characteristic;
D3 ref to AI;
D4 advantage of using AI;
D5 offspring inspected and best mated;
D6 several / many, generations;
D7 ref to problem inbreeding;
D8 ref to way of minimising inbreeding;
D9 ref to heritability;
D10 easier to select for traits with high heritability / ora;
D11 easier to select for discontinuous variation / ora continuous variation;
D12 ref to polygenes / additive effect; max 6 ‘ describe ’ D marks
explanation
E13 selective breeding involves whole genomes;
E14 hence other traits follow selected trait(s);
E15 ref to linkage;
E16 artificial selection;
E17 selection, different from natural selection / for benefit of humans;
E18 starter population, small / not representative;
A founder principle max 4 ‘ explain ’ E marks
AVP either D or E mark;
e.g. ref to use of, IVF / surrogate, with reason
ref to loss of alleles / genetic erosion max 8
QWC - legible text with accurate spelling, punctuation and grammar ; 1
[9]
65. (a) (i) cow superovulated;
treated with, hormone / FSH / named proprietary brand ;
washed out of oviduct (A uterus ) / collected from ovary;
detail washing;
detail collection ; max 3
(ii) ref to mitochondrial DNA;
detail; e.g. circular / self-replicating
mitochondria in cytoplasts fused with darted buffalo cell; A organelle
embryo has mixture of buffalo and cow mitochondria;
nuclear / chromosomal, DNA is buffalo;
ref to bacterial contamination; max 2
(iii) for correct phase of cycle;
ref to synchronisation;
to prepare uterus for (implantation of) embryo;
ref to increased thickness of uterine lining;
ref to increased vascularisation of uterine lining; max 3
(b) increases rate of reproduction;
does not require species’ eggs;
so does not require fertile female;
does not require female for pregnancy / uses surrogate;
female not put at risk in, travel / mating / pregnancy;
successfully formed embryo can be, subdivided / cloned;
can use adult cells from all existing animals to maintain diversity ; max 4
(c) sperm bank;
oocytes / eggs; “gametes” = 1 mark only
embryos;
tissue;
zoo / reserve / game park; max 3
[15]
66. (i) 4 - 6 base pairs;
palindromic / AW;
specific sequence; max 2
(ii) yes, same sticky ends / sticky ends shown; GATC / CTAG
complementary (bases);
hydrogen bond;
A with T;
C with G; max 3
(iii) two correct cuts;
G| A T T C A G A A T T T C G| A A T C
C T A A |G T C T T A A A G C T T A |G 1
[6]
67. 1 restriction enzyme to cut gene from genome;
2 and, plasmid / artificial chromosome / DNA of vector ;
3 same restriction enzyme;
4 if cut with sticky ends then join;
5 if cut with blunt ends then, sticky ends / nucleotides, added; R bases
6 with C bases one end and G bases other;
7 requires terminal transferase;
8 (DNA) ligase needed to seal nicks in DNA backbone;
9 ref to join phosphate - sugar / adds phosphate;
10 DNA may be produced by reverse transcriptase;
11 from mRNA;
12 single strand made double stranded by DNA polymerase;
13 wanted DNA replicated by polymerase chain reaction (PCR);
14 using, DNA polymerase with high optimum temperature /Taq polymerase;
15 AVP; max 8
QWC - clear, well-organised answer using specialist terms; 1
award QWC mark if three of the following are used
endonuclease
terminal transferase
reverse transcriptase
(DNA) ligase
DNA polymerase
PCR
correct use of nucleotide and base
sticky ends
blunt ends
[9]
68. (a) (i) 1 mutation;
2 random / spontaneous / chance / pre-existing;
3 natural selection;
4 drug / insecticide, is, selective agent / selective pressure;
5 resistants have selective advantage;
6 resistants survive / susceptibles die;
7 pass, allele / mutation, to offspring; R gene / resistance
8 allele frequency increases;
9 rapid because, multiplicative phase / short generation time / large
10 numbers offspring / many breeding sites; max 5
(ii) Plasmodium inside, liver cell / red blood cell;
antibodies cannot reach target / cannot be detected by immune system;
large genome;
antigenic variation / AW;
variation from meiosis;
detail; e.g. independent assortment / crossing over
parasite switches between different versions of proteins;
ref var gene; max 3
(b) (i) marks in pairs - one pair only
mutation; with lack of production;
examples
in, promoter / ‘on’ switch ; so not transcribed;
to give premature stop codon; so, no useful / shortened, product;
deletion; with loss of allele / different product;
frameshift; so, different / no useful, mRNA / product;
in initiation codon; so mRNA not translated ;
AVP mutation; AVP lack of production; max 2
(ii) marks in pairs - one pair only
no, membrane receptor / AW; so no, binding / internalisation;
no, channel / carrier / pump; so lack of essential, nutrient / ion;
do not multiply in liver; so not available to infect red blood cells;
AVP protein; problem; max 2
(c) 100% protection with 2 boosters;
irrespective of dosage;
70% with 1 booster;
no evidence with 50 000 whether works with one booster;
ref to memory cells;
needs large numbers of parasite / ref 10 000 x 3;
safe / will not cause disease / does not kill mice ;
might mutate back to wild type;
can infect liver cells even if no further development;
may need drug to remove from liver;
data relates only to mice / may not be applicable to humans;
AVP; e.g. no data comparing results with standard antigenic (AW)
vaccine max 3
[15]
69. insulin is, polypeptide / protein;
(promoter), switches on transcription or makes gene produce, mRNA /
insulin;
as blood glucose rises insulin production increases;
ref to figures with units;
only produced when needed;
ref to, homeostasis / negative feedback; max 3
[3]
70. benefits
avoids injections / pain of injections / children’s fear of injections;
mimics normal pancreatic behaviour;
more stable homeostasis / reduced highs and lows in blood sugar;
less chance, hypoglycaemia / hyperglycaemia;
less restriction on lifestyle;
no need to measure blood sugar;
AVP; max 3
problems
rejection;
cells could lodge elsewhere;
may take longer to act;
AVP; e.g. rat data may not be applicable to humans,
transgene may have unforeseen effect max 3 max 4
[4]
71. genetically isolated populations;
allopatric speciation / AW;
ref to genetic drift;
ref to, founder effect / founder population;
loss of alleles / genetic erosion / reduced gene pool / loss of genetic
diversity / AW;
ref to, disease / population crash;
AVP; e.g. ref to exposure to different selection pressures max 4
[4]
72. plot size;
soil type;
soil pH;
plant cover;
aspect / locality;
ref to temperature linked to aspect;
slope;
ref to rainfall or irrigation;
time period ;
AVP; e.g. tillage , method of cultivation, degree of compaction
AVP; e.g. previous use of land max 3
[3]
73. (i) A cartilage;
B synovial fluid; 2
(ii) reduces friction / stops bones rubbing together; R no friction
shock absorber / cushions bone;
keeps (joint) lubricated / AW;
(fluid) provides nutrients to, chondrocytes / cartilage; A cells 3 max
[5]
74. 1 cone cells absorbs light;
2 iodopsin changes form / AW;
3 ref to three different types of cone;
4 hyperpolarisation / –40mV to –70mV;
5 stops releasing transmitter;
6 bipolar / ganglion , cells;
7 action potentials / impulses, along optic nerve; max 4
8 to, visual sensory area / sensory cortex;
9 then visual association area;
10 ref to occipital lobe;
11 then temporal lobe;
12 where word is identified from memory / AW;
13 AVP; e.g. glutamate,
optic chiasma,
inhibitory action of transmitter 6 max
QWC – legible text with accurate spelling, punctuation and grammar; 1
[7]
75. chimpanzees
arboreal / AW;
co-ordination of movement more complex / chimps perform more
complicated tasks / AW; ora
more neurones required / AW; ora
AVP; e.g. hand-eye co-ordination 2 max
[2]
76. (i) red light; 1
(ii) arm withdrawn (without a shock); 1
[2]
77. 1 rat, investigates cage / tries to escape;
2 presses lever by chance;
3 food / reward, appears ;
4 ref to ( positive ) reinforcement;
5 ref to repetition;
6 associative learning;
7 AVP; e.g. trial and error 3 max
[3]
78. (i) S dorsal root ganglion;
T relay / intermediate / bipolar / internuncial, neurone; 2
(ii) 1 rapid / fast acting ;
2 short lived;
3 automatic / involuntary / no conscious thought / brain not involved;
4 not learned / innate / genetic / inborn / instinctive;
5 response the same each time / stereotypical;
6 AVP; e.g. safety / survival 3 max
(iii) 1 distortion / AW;
2 Na+, gates / channels , open ; A sodium / Na
3 Na+ / sodium ions, enter; R sodium / Na
4 depolarisation / –65mV to +40mV;
5 receptor / generator, potential;
6 ref to threshold;
7 action potential; allow only if linked to idea of threshold reached 3 max
(iv) neurotransmitter only, in presynaptic knob / released from presynaptic
membrane;
receptors only on postsynaptic membrane;
ref to refractory period / hyperpolarisation; 2 max
[10]
79. 1 eutrophication ;
2 increased growth of, algae / seaweeds;
3 block, light / space;
4 ref to competition;
5 (so) alters food chain / example;
6 decomposition of, sewage / dead organisms;
7 ref to aerobic bacteria / increased BOD / less oxygen in water;
8 fish / sea slugs / sponges / corals, die; (linked to oxygen loss)
9 AVP; e.g. increased mineral nutrients increases susceptibility of corals to
disease,
increased numbers of anaerobic species, ref to heavy metal toxicity 4 max
[4]
80. humans are eukaryotes / Escherichia coli is a prokaryote;
humans / eukaryotes have (accept ora)
larger, proteins / genes;
introns;
‘ junk ’ DNA / non-coding DNA;
repeating sequences;
centromeres / telomeres;
fossil genes;
E. coli cell much smaller; ora
selection for, less waste of space / more compact genome; 2 max
[2]
81. (i) semi- conservative replication;
DNA, polymerase / helicase;
breaks hydrogen bonds between two DNA strands / unzips DNA;
each DNA strand acts as a template / both strands copied;
complementary base-pairing (with free DNA nucleotides);
sugar-phosphate backbone forms; 2 max
(ii) crossing-over;
in prophase;
recombination of, non-sister / maternal and paternal, DNA;
AVP; e.g. matching cuts in DNA
DNA ligase 2 max
(iii) synapsis / to hold, (homologous) chromosomes / bivalent, together;
(so close enough) for crossing-over;
so can be evenly segregated;
AVP; e.g. to package or support chromosomes,
avoid DNA breaking,
easier to move DNA 2 max
[6]
82. (a) (i) mRNA leaves nucleus; ora
mRNA, translated / used to make, protein;
DNA, transcribed / used to make, mRNA;
mRNA short-term / DNA (long-term) store; 2 max
(ii) siRNA smaller / fewer nucleotides / only matches part of gene; ora
siRNA double-stranded; ora 2
(b) (complementary) base-pairing;
hydrogen bonding;
between purines and pyrimidines;
A with U; R A with T
C with G;
ref to 2 or 3 bonds (correct context); 3 max
[7]
83. (i) (CCR5 / macrophages)
(siRNAs continue to work) in long-lived cells;
only one treatment needed for macrophages / CCR5;
(siRNAs diluted) as lymphocytes divide; ora
repeat treatments needed for, lymphocytes / CD4; 2
(ii) (CCR5)
because no essential function in body / absence not a problem; 1
[3]
84. (a) do not credit if any incorrect answer included
(i) fox; 1
(ii) grass / clover / legume; 1
(b) (i) nitrogen fixation / Haber (process); A reduction 1
(ii) lightning ; A oxidation / combines with oxygen
A ‘lightening’
R thunderstorm / lighting 1
(iii) denitrifying; A correct e.g. ( Pseudomonas )
R Nitrobacter / Nitrosomonas / Rhizobium 1
(iv) fixes nitrogen / provides fixed nitrogen or NH4(+); R ammonia
ref to, clover / legume / named legume, making, amino acids /
polypeptides / protein;
(plant has) no need to rely on (fixed) nitrogen compounds in soil;
R ref to fertilisers
free- living species provide, ammonium (ions) / fixed nitrogen,
for nitrifying bacteria / nitrification; 2 max
[7]
85. (i) restriction (enzyme) / endonuclease; A named e.g. 1
(ii) (DNA) ligase; 1
[2]
86. 23 ;
6-7 ;
[2]
87. (i) A, B and E ; 1
(ii) apply ora throughout
produced by, sexual reproduction / fusion of gametes / fertilisation ;
ref to random mating ; random fertilisation = 2 marks
contain chromosomes from two individuals / diploid organisms ;
more alleles ; 2 max
(iii) C and D are haploid organisms ;
haploid cells have, one set of chromosomes / half the number of
chromosomes ;
meiosis requires pairing of homologous chromosomes ;
ref to maintaining chromosome number when gametes fuse / gametes
must be haploid ; 2 max
[5]
88. marking points 1,6 and 9 must be linked to correct statements as to what is
taking place in these stages to gain the mark.
1 prophase 1 ;
2 synapsis / homologous chromosomes pair up / bivalents form ;
3 crossing over ;
4 chiasma(ta) occur ;
5 DNA / alleles, exchanged ; A linked genes separated ;
6 metaphase 1 ;
7 independent / random, assortment ;
8 bivalents line up on equator, independent of each other / randomly ;
9 metaphase 2 ;
10 independent assortment of chromatids ;
11 chromosome mutation ;
12 named example ; e.g. non-disjunction
13 AVP ; e.g. ref to non-sister / non-identical, chromatids. 7 max
QWC  clear well organised using specialist terms ;
award the QWC mark if four of the following are used in correct context
prophase, metaphase, homologous, bivalent, chiasma, crossing over,
independent assortment 1
[8]
89. parent genotypes baby blood group
O ; mark across each line in table
B ; if no marks gained mark down columns
A ; max 2 marks if baby blood groups correct
AB ;
[4]
90. ADH / anti diuretic hormone ;
reduces blood sugar levels / correct mechanism to achieve this ;
increases blood sugar levels / correct mechanism to achieve this ;
ABA / abscisic acid ;
auxin / IAA ;
[5]
91. 1 ref to change in receptor ;
2 creates, receptor potential / generator potential ;
3 if greater than threshold value ;
4 depolarisation / AW, (of axon / sensory / afferent, neurone) ;
5 ref to action potential (anywhere in answer) ;
6 ref to, myelin sheath / myelinated neurones ;
7 saltatory conduction / AW ;
8 ref to nodes of Ranvier ;
9 synapse with, motor / effector / efferent, neurone ;
10 ref to, calcium ions / calcium channels ;
11 vesicles of neurotransmitter fuse with presynaptic membrane ;
12 named neurotransmitter ;
13 secretion / exocytosis (from presynaptic membrane) ; R release
14 diffusion across synaptic cleft ;
15 receptors on postsynaptic membrane ;
16 depolarisation / AW, (of postsynaptic membrane / motor neurone) ;
17 ref to, neuromuscular junction / motor end plate ;
18 AVP ; e.g. ion movement,
refractory period
voltage-gated channels 8 max
QWC – legible text with accurate spelling, punctuation and grammar ; 1
[9]
92. (a) (i) produced by asexual reproduction ;
one parent / no gamete formation ;
genetically identical (to parent) ;
produced by mitosis ; 2 max
(ii) keeps, desirable characteristics / high productivity / AW ;
quicker / no germination time ;
stronger / more likely to survive ;
mass production / more produced ;
disease free ; 2 max
(iii) induce seedless fruit ;
increase fruit size ;
improve fruit set ;
avoid need for pollination ;
AVP ; e.g. weedkiller / inhibits sprouting in potatoes / prevents
premature fruit drop 2 max
(iv) large surface area ;
absorbs water ;
by osmosis / down a water potential gradient ;
ions / named ion(s) ;
ions pass through cell surface membrane ;
protein, channels / carriers ;
active transport ;
help to prepare cuttings for transplanting to soil / AW ;
AVP ; 4 max
(b) sucrose ;
amino acids ;
vitamins ;
ions / named ions ;
auxins ;
cytokinins ;
water ;
agar ; 3 max
(c) labour intensive ;
sterile conditions ;
special equipment ;
trained staff ;
electricity / power, costs ;
quality control of process ;
AVP ; e.g. set up costs 3 max
(d) grafting / budding / described ;
layering / described ; 1 max
[17]
93. (a) (i) epistasis ;
dominant ;
correct ref to epistatic and hypostatic gene ;
ref to protein / enzyme / inhibitor, product of allele A ;
prevents, transcription / translation ;
inhibits, expression / gene action ;
blocks enzyme activity ; 3 max
(ii) small number of phenotypes ;
distinct (phenotypic) classes ;
qualitative ;
two genes / AW ;
large effect ;
different genes have different effects ;
not environmental ;
AVP ; 3 max
(b) (i) emasculate /remove stamens from / male sterility gene in, seed parent ;
bag flowers, before / after, pollination ;
grow in isolation ;
transfer pollen by hand ; 2 max
(ii) increase genetic contribution of that species / ora ;
keep (alleles of) background genes of that species ;
so that only A/a exchanged / AW ;
to see effect of A/a in other species ; 2 max
(iii) to produce, homozygous recessive / aa / AW ;
so that, wanted allele / desired trait, expressed ; 1 max
(c) pollinators can distinguish colour ;
bees attracted to pink ; [A refs to ‘blue’ or UV re pink]
swapping alleles reduces visits by normal pollinator ;
swapping alleles attracts wrong pollinator ;
selectively bred / aa / red M lewisii, decreases bumblebee visits;
but does not attract many hummingbirds ;
selectively bred / Aa / pink M. cardinalis, attracts bumblebees;
and decreases hummingbird visits only slightly ;
ref comparative figures ;
colour important to bees ;
colour not important to hummingbirds / some other feature important
to hummingbirds ;
AVP ; 4 max
[15]
94. more transcription by QQ genotype ;
at both ages ;
in both skeletal and cardiac muscle ;
A ‘throughout’ / ‘in all cases ’ for 1 mark of these 2
much more in skeletal muscle / slightly more in cardiac muscle ;
in QQ genotypes expression falls with age in both skeletal and cardiac muscle ;
in qq genotypes expression rises with age in skeletal but falls in cardiac muscle ;
use of comparative figures ; 4 max
[4]
95. (a) 1 gene bank ;
2 ref to wild type ;
3 maintain genetic diversity ;
4 ref to, loss of alleles / genetic erosion ;
5 may have appropriate trait for breeding ;
6 for future use ;
7 requirements of breeders change ;
8 in case , climate change / different conditions ;
9 ref to, temperature / global warming ;
10 ref to, pH tolerance / acid rain ;
11 as yet unknown traits may be useful ;
12 in case other named change ;
13 may lose trait if interbred ;
14 may form part of, food web / community ;
15 that cannot be replaced ;
16 adapted for, habitat / niche ;
17 hybrids less well adapted ;
18 ref to extinction ;
19 AVP ; e.g. need to maintain population for leisure fishing
20 AVP ; 8 max
QWC – legible text with accurate spelling, punctuation and
grammar; 1
(b) (i) enzyme from bacterium ;
break down DNA of invading (bacterio)phages ;
ref to specific site of DNA ;
detail of site (4 - 6 bp / palindromic) ;
cut DNA ;
leaving blunt ends ;
or sticky ends ; 3 max
(ii) crucian carp 1 (thick) band in correct position (see diagram) ;
hybrid goldfish x common carp 2 ( thin ) bands in correct position ;
hybrid common carp x crucian carp 2 (thin) bands in correct position ; 3
[15]
96. (a) mRNA and its complementary RNA bind together ;
hydrogen bonding ;
A to U and C to G ; R ‘T’
double stranded RNA / duplex RNA ;
cannot bind to ribosome ;
tRNA cannot bind ;
cannot be translated / AW;
ref to, RNA interference / RNAi ; 4 max
(b) (i) theobromine content, reduced / approximately halved ;
no significant difference between short and long lengths of RNA ;
caffeine content reduced ;
to half by short lengths of RNA ; A figures
to about a third by long lengths of RNA ; A figures 3 max
(ii) (re caffeine) greater chance of pairing longer length with mRNA ;
AVP ; 1
(iii) explant of meristematic / cambium / totipotent / pluripotent, cells
/ tissue ;
explant (surface) sterilised / sterile nutrient ;
appropriate hormone to stimulate, mitosis / division ;
callus formed ;
subdivided ;
appropriate hormone to stimulate differentiation ;
plantlet formed ;
hardening medium / sterile soil 4 max
(iv) genetically identical ;
genotype does not affect result ;
easily genetically engineered ;
plants derived from it identically genetically engineered / AW ;
large numbers easily obtained ;
early stages compact ; 3 max
so easily kept in identical conditions ;
[15]
97. (a) penetration of biofilm difficult ;
ref to diffusion of antibiotic ;
detail of diffusion ;
larger SA of separate bacteria / ora ;
does not reach all bacteria in film / ora ;
antibiotic trapped by film ;
detail of entrapment ;
dead bacteria in film form barrier ;
AVP ; e.g. horizontal transmission / conjugation, easier in biofilm
AVP ; 4 max
(b) both strains have identical sensitivity when in suspension ;
to all three antibiotics ;
both, less sensitive / more resistant, when in biofilms (ora) ;
strain 1 much, less sensitive / more resistant ;
comparative figures ;
C most effective / AW ;
B least effective / AW ; 4 max
(c) mutation ;
random / chance / pre-existing ;
detail of mutation ; e.g. base substitution, addition, deletion
ref to, selection / selective advantage ;
codes for different, glucan / biofilm ;
affects all three antibiotics ;
blocks antibiotic from reaching cells ;
binds antibiotics ; 4 max
(d) horizontal transmission ;
( copy of) plasmid ;
via conjugation ;
detail ; conjugation tube / ‘R’ plasmid / single strand DNA transferred
via transformation ;
transferred by (bacterio)phage ; 3 max
[15]
98. preservation of, organisms / environments ;
that are at risk from human activity ;
requires management ;
creation of new habitats ;
may need reclamation ;
conservation requires vigilance ;
resolving conflicts ; A suitable alternatives 2 max
[2]
99. (i) ( penicillin ) secondary metabolite ;
produced at start of / during stationary phase / end of growth phase ; A log
phase ref to production (at maximum ) when kept short of nutrients
/ nutrients depleting / factors limiting growth ;
continuous culture maintains in, log / rapid growth, phase ; 2 max
(ii) to provide respiratory substrate / energy ; A for respiration
to maintain culture / keep culture alive / prevent (premature) death of
culture ;
(limited) maintains in stationary phase / prevents rapid growth ;
AVP ; R glucose as carbon source 2 max
[4]
100. (i) type of starch ;
concentration of, starch / suspension ;
volume of, starch / suspension ; R amount
ref to flow rate ;
size of beads ; A number / mass / volume, of beads in column R amount
temperature ;
length / diameter, of column ;
yeast concentration ;
pH ;
AVP ; e.g. age of culture 3 max
(ii) add Benedict ’s (reagent) and, boil / heat ; A CuSO4 in alkaline solution
different, densities / colours (of precipitates) formed ; A turbidities
use of a colorimeter in correct context ;
A filtering and weighing precipitate
OR
use of Clinistix / Diastix (strips) ;
different colours obtained ;
colour compared to chart ;
accept other valid methods e.g. reference to use of biosensors 2 max
(iii) agree
not all yeast cells successfully entrapped / AW ;
(in product) yeast cells, respiring / metabolising / using sugar as an
energy source ;
(so) lower levels of sugar (in product) ;
not agree
yeast cells, entrapped (in beads) / immobilised, so product not contaminated
/ yeast not present to affect product ;
yeast cells unable to pass through, glass wool / filter ;
only very low numbers of yeast cells (so unlikely to have great effect) ; 2 max
[7]
101. (i) habituation / associative ; 1
(ii) no threat ;
no waste of energy ;
less stress ;
AVP ; 2 max
[3]
102. ref. faster / rapid / AW ;
AVP ; e.g. survival 1 max
[1]
103. (i) corpus callosum ; 1
(ii) cerebellum ;
medulla (oblongata) ;
hypothalamus ;
cerebrum / cerebral cortex ; 4
[5]
104. acetylcholine – neurotransmitter / AW ;
acetylcholinesterase – breaks down ACh / enables repolarisation of post synaptic membrane ;
[2]
105. (i) stimulus causes , increase in tension / twitch ;
fluctuation in tension / AW ;
overall increase in tension ;
AVP ; e.g. ref to figs (must have time units) 2 max
(ii) state of constant , contraction / tension ; R paralysed alone
correct ref. to heart ;
difficulty in ingestion / jaw muscles fixed ;
rib / intercostal, muscles remain contracted ;
difficulty in, lung ventilation / breathing ;
AVP ; e.g. fever / headache 3 max
[5]
106. 1 ATP produced ;
2 Na+ or K+ pump / maintains concentration gradient / repolarisation ;
transmission of impulses
3 acetylcholine / neurotransmitter formation ;
4 vesicle formation ;
5 movement of vesicles ;
6 exocytosis / vesicles fuse with membrane ;
7 ref. active transport (of ACh / Ca2+) ;
8 AVP ; e.g. ref to microtubules / endocytosis 4 max
muscular contraction
9 ATP attaches to myosin head / ATPase ;
10 hydrolysis of ATP / ATP → ADP + P ;
11 myosin head tilts / shortening of sarcomere ;
12 ATP / energy, required for detachment of myosin head ;
13 from actin ;
14 calcium pumps in sarcoplasmic reticulum ;
15 synthesis of protein (for repair, growth) ;
16 AVP ; 5 max 8 max
QWC – clear, well-organised using specialist terms ; 1
award the QWC mark if four of the following are used in correct context
acetylcholine, actin, myosin, sarcoplasmic reticulum, exocytosis,
hydrolysis, repolarisation
[9]
107. (i) higher, number / proportion / percentage / ratio / fraction, of mounds
have thyme ;
(c.f. quadrats) ora
A figs, e.g. ⅔ vs ½, 2:1 vs 1:1, 36 vs 24 1
(ii) look for a statement and a reason
use smaller quadrat ; e.g. 50 cm × 50 cm
for fair test ; AW
use grid and random numbers ;
throwing keys biased ; AW
estimate, percentage cover / abundance ; A point (frame) quadrat
may be single plants in some samples and many in others ;
bigger study area / more data ; (keep equal numbers mounds and quadrats)
improves reliability / AW ;
record other plants ;
could influence thyme ;
measure / note , abiotic variables ; A example
explanation of how named variable affects thyme ;
AVP ;
AVP ; 4 max
[5]
108. (a) (i) steep increase, for the first 1 - 2 hours / till 2.2 - 3.8 (a.u) ; A linear,
steady became constant at, 3 hours / 4.3 (a.u) ;
if no figs in description, e.g. ‘ rose then constant’ award 1 mark max 2
(ii) (increased as) enzyme working / rate of reaction high / reaction
proceeding ;
(increased as) substrate converted into, drug / product ;
(levelled off / became constant, after the) enzyme, became inactive /
was denatured;
(levelled off / became constant) because product inhibits, reaction /
enzyme ;
R references to enzyme or substrate being used up R T ºC limiting 2
(b) pH ;
degree of mixing ;
enzyme concentration ;
AVP ; e.g. ref to concentration of inhibitors 1 max
(c) max of 2 marks for predicting or explaining
P1 concentration of drug higher / AW ;
P2 rate of reaction slower / AW ;
P3 may not level off (in time scale shown on graph) ;
P4 time taken to reach the maximum yield (approximately)
doubles ; (c.f. 15 ºC)
E1 not denatured ;
E2 adapted to 5 ºC / optimum / body / usual, temperature ;
E3 ref to Q10 of about 2 ;
E4 ref to lower kinetic energy / AW ;
E5 ref to E-S, collisions / complexes ;
AVP ; e.g. ref to active site 3 max
(d) (i) (shaded amino acids) form the active site ;
substrate may not attach to the active site ;
enzyme-substrate complex may not be formed / AW ; 1 max
(ii) 44 and 66 not part of active site ;
hold, active site / 3º structure / 3D structure, in shape ; A stop denaturing
hydrogen bonds weak ;
easily broken by, vibration / heat ; A pH
disulphide bridge strong ;
not broken by heat ; 2 max
(e) nucleotide / base/ DNA, sequence codes for, protein / amino acid, sequence ;
changes DNA ; A change triplet
makes different mRNA ; A change codon
transcription ;
different tRNAs line up ; A change anticodon
translation ;
different (amino acid sequence in), enzyme / protein / polypeptide ; 2 max
[13]
109. (a) any two of the following
(monomer) not glucose ;
contains nitrogen ;
contains, sulphur ;
AVP ; R ref to branching 2 max
(b) amount of glycoprotein varies (in different cells) ;
(cells carry out) endocytosis to different extents ;
cells have different life spans / example ;
no time for polysaccharide to accumulate in short lived cells ;
number / role, of lysosomes not same in all cell types ;
AVP ; 1 max
(c) with Hunter’s syndrome, lysosomes / vesicles, might be
larger ;
more numerous ;
have different shape ;
stain differently ;
AVP ; e.g. granular cytoplasm 1 max
(d) (i) unaffected parents can have an affected child ; ora
e.g. 3, 4, 8 / 11, 12, 16, 17 ; 1 max
(ii) only males affected ; ora
mothers pass it on ; ora
on the X chromosome ;
carrier women asymptomatic / dominant normal allele masks trait ;
4 / 11 / 1, could be carriers ; 2 max
(e) there are only 3 cases / too small a sample ;
mostly female line shown ;
AVP ; e.g. pedigree of, 3 / 12, not known
progeny of, 13 / 14 / 15, not known 1 max
(f) drug must act in all cells ;
lysosomes are within cells ;
hard for drug to reach ;
if drug acts as enzyme, polysaccharide on cell membranes may be broken
down ;
tissue mechanical support would break down ;
AVP ;
AVP ; e.g. no animal model
protein drug digested in gut
rare condition (qualified), economic argument 2 max
[10]
110. (a) avoid attracting a mate of a different species ; ora
ensure reproductive isolation ; 1 max
(b) (i) diffusion ; 1
(ii) so that they do not receive oxygen constantly ;
there are mitochondria between them and the cell surface ; 1 max
(c) mitochondria / aerobic respiration / oxidative phosphorylation, inhibited
only briefly ;
oxygen concentration decreases again ;
preventing, action of luciferase / production of light ;
each flash short ; ora e.g. so not continuously lit
AVP ; 2 max
(d) active transport ; A e.g. Na+/K+ pump
protein synthesis ;
synthesis of named substance ;
movement of organelles ;
phosphorylation of glucose ;
AVP ; ; ; e.g. transcription, translation, anabolic reaction
R respiration, DNA replication, chromosome movement, mitosis 3 max
(e) cells / membranes, damaged / disrupted ;
nitrous oxide released ;
mitochondria stop using oxygen ;
oxygen, allows light production / reaches light-producing organelles ;
in unlimited quantities / continuously, so light is brighter ;
respiration / oxidative phosphorylation, ceases ;
no more, ATP / NADH2 ;
luciferin, synthesis / regeneration, stops ;
AVP ; 3 max
(f) live bacteria, respire / produce ATP ; ora 1
(g) mRNA (coding for luciferase) ; A DNA 1
[13]
111. (a) (i) (place) where, organism / animal / plant / population /
community, lives ; R things / named organism 1
(ii) role of organism in, the ecosystem / AW;
A habitat / environment / community / area / place
R population 1
(iii) living / biotic, and, non-living / abiotic, components that interact; 1
(b) population = one species
and community = more than one / all, species / population; 1
[4]
112. (i) 1 some food not, eaten / accessible; A an example
2 some, food / energy, not digested / egested / lost as faeces;
3 (some assimilated) food / energy, lost in excretion;
4 ref to decomposers;
5 (some assimilated) food / energy, lost in respiration;
6 energy lost, as heat / in movement / in metabolism;
7 small proportion energy used for, growth / material,
and is available to next trophic level; 3 max
(ii) 1 plant material difficult to digest / animal material can be digested
easily;
2 ref to, cellulose / lignin / wood;
3 no cellulase;
4 (animal) gives similar spectrum of amino acids (as consumer);
5 less of the producer available to the 1° consumer than 1° consumer
available to the 2° consumer;
6 AVP; e.g. ref to gut bacteria
ignore references to numbers of organisms eaten or size of organisms 2 max
[5]
113. (i) Q, S, P, N, M, R ; 1
(ii) accept correct names of stages
Q ; A prophase 1
M ; A anaphase 2
Q / S ; A prophase 1 / metaphase 1
S ; A metaphase 1
R ; A telophase 2 5
(iii) DNA replication ;
synthesis of proteins / named protein ; A transcription / translation
synthesis of membrane ;
synthesis of, organelle(s) / named organelle ;
respiration ;
AVP ; e.g. centrioles replicate ; 2 max
[8]
114. (i) Individual 2 - XHY ;
Individual 5 - XhY ;
Individual 6 - XHY ;
Individual 9 - XHXh ;
max 2 if sex chromosomes not shown 4
(ii) half / 0.5 / 50% / 1 in 2 ; A 1:1, 50:50 R 1:2 1
(iii) carriers have, both / H and h / dominant and recessive, alleles ; A are
heterozygous R two alleles
females have two X chromosomes / ora ; 2
[7]
115. (a) (i) curve to have peaks to right of lemming peaks and must have two
peaks between 1994 and 1996 and 1998 and 2000 respectively ;
peaks below level of lemming peaks ; 2
(ii) plenty / AW, of food ;
few / AW, predators ;
high population of alternative prey for predators ;
no overcrowding / lots of breeding sites / AW ;
less disease ;
less competition from other species ;
low environmental resistance ; 3 max
(b) interspecific
between two (or more) species ;
two named species (on lemmings) ;
intraspecific
within species ;
named species plus resource ;
if definitions of interspecific and intraspecific competition are the wrong
way around can still gain one mark for correct examples of both types
of competition 3 max
(c) maximum, size / number, of a, population / species ;
either
(supported) in a particular, habitat / ecosystem / area / environment ;
or
determined by limiting factors ; 2
[10]
116. (a) form of a gene ;
position of, gene / allele on, chromosome / DNA ; 2
(b) 1 Woodland more, dark / unbanded, snails or fewer, light /
banded, snails ;
2 better camouflaged / ora ;
3 against, leaf litter / uniform background ;
4 relevant woodland data quote on colour and
banding ;
5 Grassland more, yellow / banded, snails or fewer, dark /
unbanded, snails ;
6 better camouflaged / ora ; (only award if missed
point 2)
7 against, pale / yellow / green / variable,
background ;
8 relevant grassland data quote on colour and
banding ;
9 survivors posses advantageous alleles / ora ;
10 reproduce ;
11 pass alleles on (to, offspring / next generation) ;
12 ref to stabilising selection (in both habitats) ;
13 ref to other named selection pressure(s) ;
14 not a very mobile population or little, immigration / emigration ;
15 separate gene pools described ;
16 little mutation taking place ; A no new camouflage method over time
17 habitat stable ;
18 ref to why unfavourable alleles have not disappeared ;
19 AVP ; e.g. calculated average figures for both habitats 8 max
QWC – clear well organised using specialist terms ;
clear and well organised and must include marking points 4 and 8 1
[11]
117. (a) transmit (information) between neurones ;
ensure one way transmission of impulses ;
integration of nerve pathways ; A allows, convergence / divergence /
summation filter out low level stimuli ;
prevent overstimulation and fatigue ;
ref to inhibition ; 2 max
AVP ; e.g. role in, learning / memory
(b) vesicles move to presynaptic membrane ;
vesicles fuse with presynaptic membrane ;
exocytosis / AW ;
neurotransmitter moves across synaptic cleft ;
neurotransmitter binds to receptor on postsynaptic membrane ;
recycling of neurotransmitter / channels for uptake of neurotransmitter ; 3 max
(c) 1 to allow repolarisation to occur ;
2 by unblocking (neurotransmitter) receptor ;
3 prevents sodium channels remaining open ;
4 so more neurotransmitter can bind ;
5 new action potential is generated ;
6 to allow movement to occur ;
7 recycling of neurotransmitter ;
8 AVP ;
or
1 permanently depolarised ;
2 receptors (permanently) blocked ;
3 sodium channels open ;
4 no more neurotransmitter can bind ;
5 no new action potential / action potentials continuously fired ;
6 continuous contraction / AW ;
7 no recycling of neurotransmitter ;
8 AVP ; 2 max
[7]
118. (a) estimate of role of genotype in phenotypic variation / AW ;
heritability = VG / VP ;
when heritability high much of variation is, genetic / not environmental
/ ora ;
high heritability will result in successful selective breeding / ora ; 2 max
(b) single / major / Mendelian, gene ;
large effect ;
little environmental effect ;
dominant allele T expressed in homo- and heterozygote ;
not polygenic ;
not additive ;
discontinuous variation / not continuous variation ;
qualitative / not quantitative ; 2 max
(c) (i) triplet of bases that does not code for an amino acid ;
ATT / ATC / ACT ;
code to mark end of gene ;
code to stop transcription / ref to disengagement RNA polymerase ; 2 max
(ii) transcription halted early / AW ;
protein will, be smaller / have fewer amino acids ;
tertiary structure / 3D shape different ;
binding / affinity, different ;
protein inactive ; 3 max
ref to lac operon ;
(iii) ref to, promoter / operator / ‘on’ switch ;
allele T is regulator ;
(protein) binds to DNA ;
(protein) binds to repressor and prevents it binding to DNA ;
allows RNA polymerase to bind ;
AVP ; e.g. enzyme affecting transcription 2 max
(d) (i) tt + T / AW, increases number of tillers per plant ;
and number of branches per tiller ;
ref to comparative figures ; 2 max
(ii) inserted into genome randomly / cannot choose where it is inserted ;
may be within a frequently expressed gene ;
may be after an ‘on’ switch ;
lacks normal controls ;
AVP ; e.g. no other alleles affecting it 2 max
different promoter
[15]
119. 1 both result from changes in allele frequencies ;
2 selective breeding often faster than evolution / ora ;
3 both require selection of parents ;
4 to pass alleles to offspring ;
5 selective breeding involves artificial selection ;
6 v. evolution involves natural selection ;
7 man selective agent in selective breeding ;
8 v. whole environment selective agent in, natural selection / evolution ;
9 selective breeding for benefit of man ;
10 may be detrimental to organism / e.g. detriment ;
11 v. fitness for environment ;
12 single / few, trait(s) in selective breeding ;
13 v. whole, phenotype / genotype ;
14 AVP ;
15 AVP ; 8 max
QWC – legible text with accurate spelling, punctuation and grammar; 1
[9]
120. (i) depends on plant growth regulators ; A plant growth substances / plant hormones
named plant growth regulator ;
produced in a variety of tissues ;
may have effect at a distance ;
move, cell to cell / by diffusion / by active transport / via vascular tissue
via a named vascular tissue / via plasmodesmata ;
different effects in different tissues ;
different effects when acting together ; 2 max
(ii) coordinate, growth / development / activities , of different parts ;
respond to internal changes ;
respond to, external / environmental / e.g. environmental, change ;
AVP ; e.g. comparison with animals 2 max
[4]
121. (i) economy of, materials / resources ;
economy of energy ;
saves unnecessary, transcription / translation ; 2 max
(ii) random / chance / preexisting, mutation (for resistance) ;
resistants survive / susceptibles die ;
natural selection ;
insecticide selective agent ; A selective pressure
resistants pass, mutation / allele for resistance, to offspring ; R gene
frequency of, mutation / allele for resistance, increases in population ; 5 max
[7]
122. plant signal used by earworms ;
J switches on gene coding for E ;
can then break down insecticide ;
effect on transcription ; (× 5.5)
reduces mortality ;
even in absence of insecticide ;
in absence of J, mortality, high / c. 87% ;
ref to comparative figures ;
e.g. 87 to 48% / almost halved, in presence of insecticide
16 to 7% / more than halved, in absence of insecticide
slight expression of E in absence of J caused by insecticide ; 4 max
[4]
123. (a) rDNA = DNA from two sources ;
both DNAs cut with, restriction enzyme / named restriction enzyme ;
giving sticky ends ;
or giving blunt ends to which sticky ends added ;
complementary binding of sticky ends ;
H bonds / e.g. A to T / e.g. C to G ;
nicks in (sugar-phosphate) backbone sealed by ligase ; 3 max
(b) percentage / proportion, of, muscle fibres with central nuclei / dying muscle
fibres, increases in control with time ;
percentage / proportion, of, muscle fibres with central nuclei / dying muscle
fibres, reduced by treatment ;
ref to comparative figures with percentages and day ; 3
(c) advantages
1 can identify presence of disorder ;
2 removes uncertainty ;
3 allows early treatment ;
4 which may improve, life expectancy / quality of life ; A avoid
unncessary suffering
5 allows, informed choice about having children / planning healthy
family ;
6 allows IVF and, embryo screening / preimplantation genetic
diagnosis (PGD) ;
7 allows fetal testing and termination ;
8 choice, re donation / adoption ;
9 AVP ; e.g. detail of donation: AI(D) / egg donation / embryo
donation
maximum 5 on advantages
disadvantages
10 false , positives / negatives ;
11 may not be test for all mutations ;
12 only small number tests available / not available for all conditions ;
13 simple presence may not result in condition ;
14 confirmed presence gives stress / fear ;
15 problem re, telling / testing, rest of family ;
16 discrimination by, employers / insurers ;
17 ethics of termination ;
18 AVP ; e.g. detail of problem of test, risk of test procedure,
diagnosis and elimination rather than treatment, increase
in, intolerance / discrimination, of disabled, ‘designer’
problem maximum 5 on disadvantages
8 max
QWC – clear well organised using specialist terms; 1
must include both advantages and disadvantages and two terms
such as
life expectancy, quality of life,
IVF, PGD, PGH, AI(D),
amniocentesis,
CVS, karyotype,
false positive, false negative
[15]
124. (i) natural change in species composition (in an area) ;
ref to directional change ;
ref to named examples in the diagram (either species or category) ;
over a period of time ;
a number of recognisable stages / seres / seral stages ;
one sere changes the conditions for the next ;
e.g. depth of soil increases / soil stabilisation ;
leads to a climax community ;
creation of niches ;
ref to nitrogen fixation ;
AVP ; e.g. pioneer species 4 max
(ii) development of deeper soil ;
soil, becomes rich in humus / has more nutrients / is more fertile ;
dominant species change ;
plant species get larger / shrubs to trees / increase in biomass / larger
root systems ;
R soil structure improves unqualified ;
AVP ; 2 max
(iii) biotic = animal species / number of soil organisms / decomposers /
detritivores / decrease in biodiversity ;
AVP ;
abiotic = pH of soil / nitrogen or mineral content of soil / soil texture
/ wind speed / humidity / shading / light intensity / soil
water retention ;
AVP ; e.g. temperature 2 max
[8]
125. award marks if diagram clearly annotated
reservoir for storage of nutrients ;
ref to method for addition of nutrients and removal, of waste / products ;
A substrate
ref to more detail of, nutrient addition / product removal, at a constant rate /
continually / throughout fermentation period ;
idea of rate of product removal equal to addition of nutrients ;
A keep volume constant
use of probes / sensors / monitors ; A thermometer (for temperature)
(to monitor) any two of, temperature / pH / oxygen levels ;
method to maintain pH e.g. use of buffers, tube to add acid / alkali ;
addition of antifoam ;
ref. to need to maintain sterility (to avoid contamination) ;
method to maintain constant temperature e.g. (thermostatically-controlled) water
bath , cooling jacket ; R heat exchanger
AVP ; e.g. use of stirrer, method to avoid, clumping of cells / blocking of inlet or
outlet pipe (s) 4 max
[4]
126. any three acceptable e.g.
disease / virus, free ;
genetically identical / clone ;
maintain, favourable characteristics / advantageous phenotypes ;
faster method ;
produces many plants ;
allows long-term storage of plant tissue ;
easily genetically manipulated / example of genetic manipulation ;
easier exchange between countries as no quarantine ;
enables optimal production of useful secondary products (e.g. codeine
from poppy) ;
no external environmental influences ;
no influence of seasonal variation ;
AVP ; e.g. use for, sterile / infertile, plants,
AVP ; named example of advantageous phenotype e.g. grow more vigorously
use for rare or endangered plants
relevant example of genetic manipulation 3 max
[3]
127. answers referring to insulin production can also be credited in mp 2,3,4
1 Escherichia coli ; A E. coli
genetic engineering 3 max
2 amino acid sequence (of HGH), known / analysed ;
3 gene coding for HGH synthesised ;
4 using, triplet code / genetic code ;
OR
5 mRNA (coding for insulin) from beta cells ;
6 use reverse transcriptase ;
7 synthesise cDNA ;
5 plasmid (vector) ;
6 cut using restriction (endonuclease) enzyme ;
7 ref to gene and plasmid mixed with (DNA) ligase ;
8 (recombinant) plasmid introduced into, bacterium / bacteria ; AW
large scale production 4 max
9 genetically engineered / recombinant bacteria ;
10 grown in fermenter / fermentation, qualified ;
11 reproduce / replicate / multiply / undergo binary fission / form a clone
/ large numbers / millions of bacteria / gene cloning ;
12 idea of gene expression / transcription and translation, for HGH,
synthesis / production ; A insulin when relevant
13 downstream processing ;
14 separation / purification, of growth hormone ; A insulin when relevant
15 AVP ; e.g. ref to screening using antibiotic resistance markers
16 AVP ; scaling up to determine optimum operating conditions
bacteria killed and separated (from proteins)
by centrifugation
growth hormone separated from other, proteins / molecules
(product separated by) large scale chromatography / ultrafiltration
other detail of fermentation e.g. pH 5.5 – 8.0, temperature
20 – 45 ºC, aeration, glucose
doubling time 20 minutes 6 max
QWC – clear, well organised with specialist terms ; 1
any three, used in context, from
amino acid sequence (beta cells for insulin) / triplet (mRNA for insulin) /
genetic code (reverse transcriptase for insulin), plasmid, vector, restriction
enzyme, ligase, recombinant, genetically engineered, binary fission, clone,
transcription, translation, downstream processing, screening, antibiotic
resistance markers, centrifugation
[7]
128. surrounded by meninges ;
cerebrospinal fluid ;
absorbs shocks ;
brain protected by, cranium / skull ;
spinal cord protected by vertebrae ; 3 max
[3]
129. (i) time taken (to make choice) decreases ;
as number of trials increases / AW ;
ref to figures ;
idea chamber B chosen more often towards end of investigation ; 2 max
(ii) same, apparatus / conditions ;
different experimental mouse ;
idea of same species / same age / same gender, of (experimental) mouse ;
no companion mouse / B and C empty ;
same number of trials ;
AVP ; 3 max
(iii) time taken does not decrease significantly ;
roughly equal choice of chamber B or C / AW ; 1 max
(iv) trial and error learning / operant conditioning ;
ref to associative learning ;
companion animal is, reinforcer / reward ;
no conditioned stimulus ;
no conditioned response ;
AVP ; 3 max
[9]
130. (a) plasmid DNA protein
nucleotides / sugar + phosphate + base ; amino acids ;
4 different subunits ; 20 different subunits ;
phosphodiester bonds ; A phosphoester peptide bonds / polypeptide ;
contains P ; contains S / disulphide bonds ;
double-stranded / double helix ; may have 4º structure ;
circular ; ref to, 2º / 3º, structure / AW ;
AVP ; e.g. role of H bonds 3 max
(b) (i) stimulates, immune response / production of antibodies / T or B cells ; 1
(ii) stimulate, cell-mediated immunity / T cells ;
antigen, remains in body longer / continuously produced ;
antigens in blood only stimulate, humoral immune system / B cells ;
antigens (in blood) lost in urine / broken down in liver ;
ref to MHC ; 1 max
(c) (i) binds RNA polymerase ;
allows, transcription / production of mRNA ;
switches gene on / allows gene expression ; 2 max
(ii) ( protect against) more than one, strain / disease / pathogen / AW ;
stronger immune response ;
less likely mutant form will escape immune response / AW ;
AVP ; cheaper / reduces number of vaccinations 2 max
(iii) Golgi modifies protein / polypeptide / AW ;
forms glycoproteins / add sugars or carbohydrate ;
Golgi forms vesicles ;
incorporated into cell membrane ; R exocytosis
AVP ; 2 max
(d) cells that take up DNA vaccine might
1 function less well ;
2 be killed by immune system / trigger auto-immune response ;
3 have genes disrupted / mutation ;
4 new gene might be inherited / AW ;
5 plasmid could enter bacteria ;
6 superbug / create new disease / AW ;
7 effects unknown / new technology / no human trials ;
8 AVP ; ref ethics, ref irreversible 3 max
[14]
131. U;
V;
Z;
S; 4
[4]
132. (a) (i) AaBB white;
aaBB black;
Aabb white;
aabb brown ; 4
(ii) (dominant) epistasis; 1
(iii) codes for inhibitor;
protein;
blocks transcription (of allele coding for pigment );
ref to, regulator / promoter;
blocks enzyme (producing pigment);
AVP; e.g. detail max 3
(b) (i) AaBb × AaBb / AaBb × Aabb;
both must have A because they are white;
* both must, have a / not be homozygous AA, because some
kittens coloured;
* both must have b to give brown kittens;
• ‘must be heterozygous at both loci’ = 1 only
at least one / one or both, must have B to give black kittens;
credit ref to Punnett square showing genotypes;
credit ref to Punnett square showing phenotypes; max 5
(ii) AaBb × AaBb 12 white : 3 black : 1 brown;;
AaBb × Aabb 6 white : 1 black : 1 brown;; max 2
[15]
133. (a) (i) gradual process / AW;
to improve traits;
to achieve homozygosity / AW;
best in each generation interbred;
ref to artificial selection;
ref to several traits involved / may be, additive / polygenic; max 2
(ii) ref to mitosis;
chromosomes replicated;
failure of, spindle / cell division; max 2
colchicine / other method;
(iii) self-pollination prevented;
pollination by foreign pollen prevented;
pollen transfer;
practical detail; max 2
(iv) 3n;
meiosis fails;
ref to, synapsis / homologous pairs; max 2
(b) (i) sterile explant;
sterile nutrient medium;
ref to plant growth regulators;
callus;
subdivided;
medium with different plant growth regulators;
plantlets / embryoids;
hardening medium / sterile soil;
AVP; e.g. appropriate plant growth regulators max 5
(ii) callus can be divided ;
large numbers of identical plants; A clone
in short time;
bulk up sterile hybrid;
bulk up master hybrid lines;
no need for making more 4n; max 2
[15]
134. A / ‘marbling’;
scale 0 – 1;
measure of genetic v. environmental contribution;
high value most easily selected for;
value growth rate>subcutaneous fat>‘rib eye’; max 3
all the traits / even ‘rib eye’, can be selected for;
[3]
135. increase in use of, GM crop / GE crop / Bt cotton ;
no / less, insecticide needed;
reduced number of cases of pesticide poisoning;
ref to figures (e.g. by × 4.4);
reduced cost (insecticide);
ref to figures (e.g. by 0.62 US$ kg-1 / × 1.38);
ref to limitations of survey;
AVP;
A reverse arguments max 4
[4]
136. (i) ref to, rDNA / recombinant DNA;
restriction enzyme(s);
cut DNA at specific site(s);
detail site(s);
ref to viral DNA and, human DNA / DNA of gene;
ref to sticky ends;
complementary binding;
detail of binding; A = T / C = G / hydrogen bonds
ligase to seal ‘nicks’ in (sugar-phosphate) backbone; max 4
(ii) has effect when added to genome;
not masked;
no need to, remove / inactivate, recessive / mutant, allele; max 2
[6]
137. (i) trees are living organisms;
renewable;
ref to, growth / growing;
timber is, of use to human beings / made into products; max 2
(ii) harvested at levels which leave sufficient organisms;
to grow / reproduce, and replenish what has been harvested;
ref to, coppicing / replanting / afforestation;
can be carried on indefinitely; max 2
[4]
138. (a) cyclamen mite / prey populations increase;
when conditions are suitable / when predator numbers are low / no or
few limiting factors;
provides plenty of food for predator mites;
which begin to increase later / time lag;
cyclamen mites are then eaten by (increasing numbers of) predators;
so both decline in numbers;
cycle repeated;
prey populations reach higher levels than predators; max 4
(b) (i) start by looking at end of February
increases with appropriate time lag;
decreases at spraying times (end of June / beginning of October);
final peak for predator numbers is the lowest; max 2
(ii) less food available / less strawberry plants;
low temperature / frost;
other predators;
disease / parasites;
ref to parasitoids;
AVP;
R spraying idea max 2
(c) (i) biological (pest control); 1
(ii) insecticides, are harmful to other organisms / may kill natural
predators to the pest;
reduces species diversity / disrupts food chains;
many insecticides are, slow to biodegrade / long lasting;
concentrate along food chains / bioaccumulate / bioconcentrate;
stored in fat deposits of organisms;
ref to effects on top carnivores; e.g. egg shell thinning
poisonous to those applying them; A ref to humans / asthma sufferers
pests can build up a resistance;
ref to selection;
run-off from land carries them into water supplies / causes pollution /
poisons aquatic organisms;
problems of residues in food;
AVP; e.g. pesticides need to be used repeatedly max 5
(d) crop rotation;
intercropping;
release of, irradiated / sterile, males of pest species;
AVP; e.g. fly paper max 2
[16]
139. (a) trees felled for wood to, sell / export ;
cleared to provide land for agriculture ; A cattle ranching
to build, housing / villages;
industrial development / mining / quarrying;
building of roads; max 3
(b) 1 high, biodiversity / species diversity;
2 deforestation , causes extinction / reduces biodiversity;
3 decrease in, size of gene pool / genetic diversity;
4 act as carbon, reservoirs / sinks ; R carbon fixation
5 remove carbon dioxide from atmosphere;
6 release of carbon dioxide when wood is burnt;
7 less photosynthesis also means less oxygen production;
8 transpiration contributes to atmospheric water content;
9 destruction of rainforests disrupts water cycle;
10 rainforests can be used to supply sustainable crops;
11 example of crop; e.g nuts / rubber / fruits / plant oils
12 drugs / other useful compounds (may await discovery), that only
occur in rainforests;
13 soils are nutrient deficient and cannot sustain agriculture;
14 increased risk of soil erosion;
15 moral responsibility to conserve for later generations;
16 ref to indigenous populations / tribes ;
17 AVP; e.g. provision of habitats
ref to Fig. 1 max 8
QWC – clear, well organised using specialist terms; 1
award the QWC mark if four of the following are used in correct
context
biodiversity transpiration
deforestation water cycle
carbon reservoirs / sinks sustainable
photosynthesis nutrient deficient
(c) ban on import of wood from, tropical rain forests / unsustainable sources;
introduce labelling system for wood;
trade sanctions on countries that continue to remove rain forests;
schemes / financial support, for setting up of sustainable use of rain forests;
development of ecotourism;
educate local population as to importance of rain forests;
forest reserves established ;
AVP;
AVP; e.g. debt relief
fair trade schemes
quotas max 3
[15]
140. (a) advantages (max 2)
can be used with any species (irrespective of size);
does not require to distinguish one individual from another ;
quick to assess; R simple
disadvantages
subjective / AW;
dominant species may be over-estimated; max 3
(b) (i) line established, from shore to dune slack / from… to…;
quadrat used;
suitable size / actual size stated (minimum 0.25m2); R if no units
given
placed continuously / at specified intervals along line;
key to identify species;
abundance recorded in each quadrat;
bare ground recorded; max 4
(ii) 1 ACFOR scale converted to numerical scale;
2 reading at each site recorded (on graph paper);
3 width of diagram related to ACFOR (maybe shown on diagram);
4 points from each site joined together;
5 repeated for each species found present; max 3
(c) use of, thermometer / probe ;
probe must be calibrated;
pushed into, sand / soil, to same depth each time;
repetitions at each sampling point; max 2
(d) (i) a stage during the process of succession; 1
(ii) sea couch / marram grass, grow in bare sand;
dune builds up / stabilised by grasses;
OR
colonisers established on bare, rock / soil;
example; (if not sand dunes)
ref to pioneer species;
organic matter builds up / humus content increases;
forming soil / depth of soil increases;
other species take over from grasses; A named example
from Fig. 1
roots stabilise soil structure;
diversity of species increases;
climax eventually reached;
AVP;
AVP; e.g. reference to deflected succession,
growth of shrubs max 4
[17]
141. (a) (i) penicillin; A other named antibiotic 1
(ii) (complex organic molecules) produced after / not produced during,
the (log / rapid / main) growth phase;
not essential for normal, cell growth / reproduction; max 1
(iii) batch / fed batch; 1
nutrients only added at start;
short / rapid, growth phase;
required product made, during stationary phase / late in life
cycle; ora
R death phase
shortage / depletion of, nutrients / named nutrients;
cell division / reproduction, no longer occurring;
ref to addition of, glucose / lactose, at intervals
(to avoid death of culture); max 2
(b) 1 air pressure will push the medium into the culture vessel ;
2 medium / nutrients, added to the culture at a constant rate / AW;
3 algae / cells / Chlorella, removed / harvested, from the sample port;
4 at the same rate as / to match, the nutrients added;
5 so volume in fermenter remains constant;
6 removal of, waste / toxic products;
7 that could affect, growth / reproduction;
8 (cells kept in) exponential / log / rapid / main, growth phase;
9 algae are photosynthetic;
10 light energy required;
11 ref to use of fluorescent light to avoid overheating;
12 ref to monitoring temperature;
13 ref to optimum conditions; A ‘conditions for maximum growth’
14 air bubbles to mix culture with nutrients / AW;
15 air bubbles to allow algae to get sufficient light;
16 air bubbles provide oxygen for (aerobic) respiration;
17 and CO2 for photosynthesis;
18 air flowing into the culture vessel flows out through an outflow tube;
19 preventing build-up of pressure;
20 AVP; e.g. sampling to check for mass of Chlorella max 6
(c)
heating / cooling, qualified;
foaming;
blocking of, inlet / outlet, tubes;
difficulties with, mixing / stirring;
contamination / keeping it sterile;
conditions need to be continuously monitored;
nutrient requirements may change;
AVP;
AVP; e.g. algal growth on glass
difficulties in providing sufficient light
errors lead to loss of several days production of Chlorella max 4
[15]
142. (i) RNA(i) combines with mRNA;
e.g. of base pairing (but not T) A-U / G-C;
stops translation;
ref to stops mRNA combining with ribosomes;
stops protein synthesis; max 3
(ii) chemicals / enzymes in, mouth / toothpaste / bacteria;
denature / degrade, RNA;
RNA not normally taken up by bacterial cells;
short life of RNA;
RNA not replicated in bacteria when bacteria reproduce;
toothpaste in mouth only for short time;
AVP;
AVP; e.g. washed away by saliva max 2
[5]
143. (a) (i) amylase ; 1
(ii) glycosidic; R glucosidic 1
(iii) alpha / α; 1
(b) (i) encapsulation / trapped in alginate beads;
adsorption or stuck onto, collagen / clays / resins;
cross linkage or covalent / chemical bonding to, cellulose (fibres);
gel entrapment / trapped in silica gel;
partially permeable membrane microspheres; max 2
(ii) does not mix with / does not contaminate / stays separate from, the
product; ref to, no / less / easier, downstream processing;
recoverable / not lost during processing;
reusable / cost effective;
matrix stabilises / protects the enzyme;
so activity not affected by changes in, temperature / pH or run at
a high temperature / wider range of pH;
longer, use / shelf-life;
so suitable for continuous culture / cost effective / greater yield;
AVP;
points can interchange if valid max 4
(c) not necessary to start with a pure enzyme;
keeps the enzyme away from oxygen;
more enzymes involved;
cell produces enzymes;
AVP; e.g. enzyme(s) may be, expensive / difficult to isolate
simultaneous processes can occur max 2
[11]
144. (a) (i) automatic
requires no (conscious) thought / AW;
(ii) stereotyped
carried out by all individuals in a species / always carried out in
same way / AW;
(iii) conditioned
(response) can be, modified / produced, following exposure to ‘new’
stimulus / AW; 3
(b) A any response, provided correct stimulus is given;
R non-mammalian example R examples of conditioned reflexes 1
(c) D1 time spent in box decreases as number of trials increases / AW;
D2 greatest change in response occurs in first few trials;
D3 little / less, change in response time;
D4 between trials 6 and 20;
D5 ref to supporting paired data;
D6 ref to ‘fluctuations’; max 4
E1 (at first) cat pulls, loop accidentally / AW;
E2 ref to trial and error;
E3 freedom is a, reward / reinforcer;
E4 associative learning;
E5 detail (of associative learning);
E6 pulls loop sooner / AW;
E7 correct ref to acclimatisation period
(when cat placed in box) / AW;
E8 AVP; e.g. other behaviours / inactivity, not,
reinforced / rewarded max 5 max 7
QWC – legible text with accurate spelling, punctuation and
grammar; 1
(d) no reward / punishment (of behaviour), in classical ; ora
one stimulus in operant / two stimuli in classical;
AVP; max 2
[14]
145. (a) cerebellum
coordination of, (voluntary) movement / skeletal muscles;
(control of) posture;
(control of) balance;
AVP; max 2
medulla oblongata
initiation / control of, breathing rate;
control of heart rate; R initiation of heart rate
control of blood pressure;
control of peristalsis (in alimentary canal );
AVP; max 2
(b) (i) build up of, tau / protein; 1
(ii) secretion of / high levels of, Aβ42 / beta amyloid 42
/ abnormal Aβ; R Aβ40 1
(c) similar shape to, acetylcholine / ACh;
binds to / enters, active site;
prevents ACh entry ;
competitive (inhibitor);
different shape to ACh;
enters / binds, but not at active site;
allosteric / indirect;
change in, tertiary structure / shape of active site;
non-competitive (inhibitor); max 3
(d) prevents ACh breakdown / increase ACh level;
ACh binds to, proteins / receptors;
on post-synaptic membrane;
depolarisation / action potential / impulse (produced;
activates memory circuit / AW; max 2
(e) control group;
given, placebo / tablet / injection / no drug;
idea of ‘double-blind’ trial, i.e. neither patient nor doctor aware of which
treatment each patient receives;
random assignment of each patient to one group;
similar severity of symptoms before trial;
control of age;
control of gender;
control of diet;
control of drug, dosage / administration;
not taking any other, drug / medication;
ref to suitable sample size;
AVP; max 3
[14]
146. (a) 1 : 2 :1; 1
(b) 1 ref to, codominant / equally dominant (alleles);
A incomplete dominance but R genes as alternative to alleles
2 appropriate symbols for two codominant alleles; eg G1 and G2
R a capital and a lower case symbol or two different letters
such as G and Y
3 parent plant shown or stated to be heterozygous; A if it is explained
that any sunny plant is heterozygous
4 gamete genotypes shown appropriately;
5 correct offspring genotypes;
6 the ‘Sunny’ / yellow-green, were heterozygous / genotype shown
by diagram;
7 the dark green / the yellow, were homozygous / genotype shown
by diagram; max 5
(c) 1 ref to, randomness / chance (sampling);
2 ref to random fertilisation;
3 totals are ( quite ) a large sample, pot B / single pot / six, is a small
sample;
4 if (only) six seeds, there is a greater chance of departing from an
expected ratio / AW;
5 probability of six seedlings all the same is ½ × ½ × ½ × ½ × ½ × ½;
6 with, many seedlings / the totals, the deviations of the individual
results cancel out;
7 some departure from an expected ratio is always likely / idea;
8 only the yellow number (33) deviates from the expected / 28
is half 56;
9 chi squared test could be used;
10 AVP; max 3
(d) credit ora here
A chloroplast as alternative to chlorophyll
yellow seedlings have, no / very little, chlorophyll;
cannot photosynthesise;
die when, energy reserve / carbohydrate (accept food), in seed is
exhausted;
dark green grow more because they have more chlorophyll
(than the yellow-green);
so dark green have more, photosynthetic products / named product;
ref to competition between the seedlings;
ref to, selection / selective advantage; max 3
[12]
147. (a) dissolve / destroy , cell membranes (idea); 1
(b) block the receptor / prevent ACh from binding;
no longer able to stimulate post synaptic membrane;
muscle fibres, not stimulated (by nerve fibres) / do not contract; A tetany
idea
AVP; e.g. ref to lack of synaptic transmission max 2
(c) toxin acts too fast, for immunity / antitoxin to develop (idea);
human unlikely to have been, bitten before / exposed to toxin or antigen;
one / a / few (immature), lymphocyte(s) / stem cell(s)
(able to bind the toxin);
these must be stimulated to divide / ref to clonal selection or clonal
expansion;
mitosis takes too long;
has no memory cells;
AVP; max 2
(d) more, antibody-secreting cells / B lymphocytes, produced;
enough / more, antitoxin produced; (idea of good yield)
faster / goes on for longer;
secondary response;
more mitosis (of antibody producing cells);
second injection of toxin would result in clonal expansion;
ref memory cells;
AVP; e.g. large dose would kill the horse max 3
(e) antibody / antitoxin, only remains in, blood / body, for short time;
acquired immunity / passive immunity;
person not themselves producing any antitoxin;
no clonal selection;
no memory cells;
immune system will (soon) reject / destroy the (foreign) horse antibody;
AVP; e.g. further detail explaining why immune system not stimulated
different snakes have different toxins max 2
[10]
148. 1 sun is the energy source (for the system);
2 producers / (green) plants, trap / use / absorb (sun’s energy);
3 photosynthesis;
4 not all energy trapped and reason;
5 energy used for, plant metabolism / plant processes / e.g.; A respiration
6 so this energy not, passed on / available, to consumer;
7 (some energy) used for, growth / storage;
8 so this energy is, passed on / available, to consumer;
9 1o consumer / herbivore, eats, producer / plant;
10 some producer, not edible / not accessible / e.g.;
11 some, not digested / egested / lost as faeces;
12 2o consumer / carnivore / omnivore, eats, 1o consumer / herbivore;
13 some parts of animal not edible / e.g.;
14 energy used by animal in moving (to feed );
15 energy, used / lost, in, digestion / excretion / sweating /
e.g.; A respiration
16 transfer / loss, to, decomposers / bacteria / fungi / saprotrophs;
17 energy lost as heat from respiration;
18 net productivity = gross productivity – respiration;
19 some ref to estimate of efficiency of transfer (a general statement);
20 quote of (comparative) figures from diagram;
21 manipulation of figures to illustrate a point; NOT 6612 and 14198
22 AVP;
23 AVP; e.g. loss out of ecosystem
another manipulation of figures
available energy limiting length of chain max 9
QWC – legible text with accurate spelling, punctuation and grammar; 1
[10]
149. cheaper;
ref to compatibility / less chance of rejection / fewer side effects;
stated ethical issue; e.g. don’t need to kill animals / removes religious
objections
ref to contamination / easier to purify / ref to disease;
consistent quality;
more effective (as human in origin );
production level can meet demand / reliability of supply / faster production;
ignore greater production 2 max
[2]
150. (i) restriction (enzyme) / endonuclease; 1
(ii) this may be answered in the context of inserting into a plasmid.
cut DNA with restriction enzyme;
ref to sticky ends;
complementary;
base pairs / CCC and GGG / C pairing with G / alternative;
(DNA) ligase / ligation;
ref to bonding / AW; e.g. hydrogen or phosphodiester / sugar-phosphate
AVP; e.g. add sticky ends to blunt ends
cut both at the same place 3 max
(iii) codes for, protein / polypeptide / enzyme;
A ref to, protein synthesis / transcription / translation
(enzyme) catalyses / causes, condensation / formation of glycosidic
bonds / reaction (between, mannose / sugars); 2
[6]
151. 1 genetic, testing / screening;
2 for inherited disease / AW;
3 (test to see if) individual is carrier;
4 premarital testing / predict if (potential) offspring may inherit the disease;
5 antenatal testing;
6 ref to termination;
7 embryo selection (to ensure embryo healthy); R selection of sex
8 (test for genes that contribute to) diseases that develop later in life;
9 those with genes given, advice to limit effects / counselling;
10 faster / earlier, diagnosis;
11 develop more, effective / efficient, drugs (to combat disease);
12 drugs have direct effect, on genes / protein made from specific gene code;
13 gene therapy / correct the base sequence of faulty gene;
14 economic implications / AW;
15 AVP; e.g. ref. to method used / use of gene probes / biopsy
16 AVP; allows targeting of drug treatment 4 max
[4]
152. anxiety about (future) health / may not want to know / AW;
many diseases we can test for have no treatments;
discrimination by employers;
discrimination by, insurance companies / banks;
reliability of tests in question; A false, positive / negative, result
example of disease given in context;
cost to, NHS / government ;
rich people can benefit / poor will not benefit;
AVP;; e.g. moral issues associated with embryo selection
eugenics
parents feelings towards child
presence of allele may not cause disease / ref to multifactorial
diseases
ref to storage of data and freedom of information / invasion
of privacy / question of paternity
R ‘ playing God’ / cloning 4 max
[4]
153. parental genotypes RrBb × Rrbb;
gametes RB Rb rB rb Rb rb;
offspring genotypes RRBb RrBb (RrBb) Rrbb RRbb (Rrbb) rrBb rrbb;
offspring phenotypes rough black rough white smooth black smooth white;
expected ratio 3 : 3 : 1 : 1;
accept correct gametes, offspring genotypes and offspring phenotypes in
Punnett square
use ecf except for ratio Reject the ratio 6 : 6 : 2 : 2
ratio not a stand alone mark – there must be some correct working to support it
[5]
154. (i) length of DNA;
codes for a (specific), polypeptide / protein / RNA;
found at a, locus / particular position on, a chromosome; 2
variety / form of a gene; R type of gene A type of a gene 1
(ii) assume the allele = coat colour allele
(coat colour) gene / alleles, only on X chromosome;
A no (coat colour), gene / allele, on Y chromosome
male cats, XY / only have one X chromosome;
(males have) only one (coat colour) allele / cannot have two
(coat colour) alleles;
need black and orange alleles for tortoiseshell colour; max 2
[5]
155. 1 ref to operon;
2 normally repressor substance bound to operator;
3 prevents RNA polymerase binding (at promoter) / prevents transcription;
4 lactose binds to repressor;
5 changes shape of protein molecule;
6 unable to bind (to operator);
7 RNA polymerase binds (at promoter) / transcription occurs
/ genes switched on;
8 production of lactose permease;
9 production of beta – galactosidase;
[5]
156. (a) RR RR - low, do not have enough vitamin K in diet / ref to figures;
RRRS - high, (warfarin resistant) and have enough vitamin K
/ ref to figures;
RSRS - low, will be killed by warfarin / ref to effects of warfarin;
If quote probabilities for survival less than 50% is low and over 50% is high 3
(b) (i) mutation / named mutation;
change in DNA base sequence; max 1
(ii) variation within population;
some individuals produce enzyme not susceptible to warfarin;
these individuals survive / selective advantage;
reproduce / breed;
pass, resistance / advantageous allele, to offspring; R gene
those without resistance die;
ref to selective pressure of warfarin; max 5
(c) does not directly involve humans;
environment selects individuals that will reproduce; max 1
(d) resistant allele / RR, will decrease and, susceptible allele / RS, will
increase;
RRRR at a disadvantage due to vitamin K requirements / RSRS at
an advantage due to warfarin being removed;
A frequencies of both alleles will stay the same;
must be linked to second statement
no longer any selective pressure / no directional selection; max 2
[12]
157. (a) B;
C;
D;
A; 4
(b) (i) award two marks if correct answer (26.18 / 26.2 / 26) is given
24 × 60 = 1440 ÷ 55;
26.18; A 26 / 26.2 2
(ii) less oxygen / ora;
reduced amount of nutrients / ora;
ref to pH / ora;
competition from other bacteria / interspecific competition / ora;
use of antibiotics;
AVP; ref to intestinal enzymes or immune system
R reference to temperature
treat toxins as neutral max 3
[9]
158. (a) (i) Aabb - pink;
aaBB - green; 2
(ii) (dominant) epistasis;
ref to, epistatic / hypostatic, gene;
ref to, promoter / gene switching;
increased, transcription / expression; max 3
AVP; enzyme to alter pigment / change structure of pigment /
make more pigment / complementary action
(b) (i) parents (AaBb) red spines × (aabb) green spines;
gametes AB Ab aB ab × ab; A from Punnett square
offspring genotypes;; minus 1 for each of first two mistakes
phenotypes related to genotypes; A key
ratio 1 red spines : 1 pink spines : 2 green spines; max 5
gametes AB Ab aB ab
ab AaBb Aabb aaBb aabb
red spines pink spines green spines green spines
(ii) many AaBb and aabb;
ref 1 : 1 ratio of these;
ref linkage;
ref parental types;
few Aabb and aaBb;
ref 1 : 1 ratio of these;
ref recombinants;
ref crossing over;
many red and green spined;
few / no, pink spined;
1 : 1 green : red / more green than red;
ref proportions depend on how close, loci / genes, are; max 5
[15]
159. (a) 1 prevent, self-pollination / unwanted pollination, of flowers;
2 detail of prevention;
3 cross-pollinate two varieties ; A crossed / mated / hybridised
4 detail pollination;
5 isolate, plants / flowers;
6 collect seeds and sow;
7 in high salt concentration;
8 select plants, which survive / can tolerate, high concentration;
9 and have large, tasty tomatoes;
10 interbreed these plants;
11 repeat selection;
12 ref many generations;
13 cross with variety with large tomatoes to improve size;
14 cross with variety with good flavour to improve taste;
15 ref backcrossing with original variety for salt tolerance;
16 AVP;
17 AVP; max 8
e.g. ref background genes / hybrid vigour / heritability /
effect on vigour / ref setting up pure-breeding initial lines
QWC – legible text with accurate spelling, punctuation
and grammar; 1
(b) (i) active transport;
(energy from), ATP / respiration;
against concentration gradient;
ref binding site for ion / AW;
ref change of shape of protein; max 3
(ii) GE quick(er) / SB slow(er);
(tolerance) in one generation (v. many generations);
ref one gene / rest of genome unaltered (v. hybridisation);
background genes intact (v. need for backcrossing);
different varieties engineered for different conditions;
no problem re interbreeding;
can select, transporter system / AW, / from, another species
/ named taxon;
can select, transporter system / AW, / for maximum efficiency;
AVP; max 3
[15]
160. (i) mutation;
chance / random / preexisting;
insecticide acts as selective, agent / pressure;
susceptibles die / resistants survive;
resistants pass, mutation / allele, to offspring; A gene max 3
(ii) mosquito is vector; A carrier
obligatory / AW;
part of life cycle is in mosquito;
not killed by insecticide; max 2
[5]
161. (i) DNA from two different sources;
combined / joined / AW; 2
(ii) restriction enzymes cut DNA;
at specific sites;
detail of sites;
may give sticky ends;
complementary sticky ends join;
terminal transferase / enzyme, adds sticky ends;
ligase joins, gaps / nicks; max 3
[5]
162. (i) fewer genetically engineered mosquitoes pass parasites across midgut
; A figures
fewer g e mosquitoes have parasites in salivary glands; A figures
fewer g e mosquitoes can infect (uninfected) mice; A figures
‘less good as vectors’ instead of all of first three points = 1 only
use of comparative figures; max 3
(ii) benefit one of following;
reduce use of, insecticide / drug
safer than, insecticide / drug
AVP max 1
hazard one of following;
parasite may develop resistance
gene may pass to other species
AVP max 1
[5]
163. (i) anaerobic conditions encourage denitrifying bacteria;
convert nitrate ions to (gaseous) nitrogen;
reduces available nitrogen;
sundew does not rely on, soil nitrate / soil nitrogen;
ref to, hydrolysis / digestion / use of enzymes, on insect proteins;
releasing amino acids;
ref to deamination; max 3 max 4
(ii) Reduces amount of air in soil;
roots starved of oxygen;
respiration becomes anaerobic;
insufficient energy released;
not able to absorb (enough), ions / named ion;
via active transport; max 3
[7]
164. (a) set out a grid in each area or site / description of how the grid is
established;
use random numbers;
how generated; e.g. random number tables / use of calculator
to give co-ordinates;
at that point / co-ordinate, measure nearest plant;
repeat (14 times); max 4
(b) (i) total heights;
divided by the number of plants (in the sample);
provides an average height for the sample; max 2
(ii) measure of, variability / spread of heights (in sample); R range
sum of differences from the mean;
68% of values lie within mean ± 1 S.D.;
95% of values lie within mean ± 2 S.D.; max 2
(c) greater spread from mean in site B / ora; R range
height of plants in site B is more variable / ora; max 1
(d) (i) that there is no significant difference;
between the mean height in site A and the mean height in
site B; A results any difference is entirely due to chance; max 2
(ii) there is a significant difference between the means at the two sites;
the difference is due to something other than chance;
reject the null hypothesis;
with 28 degrees of freedom;
at the 5% confidence level; A p