Cats
The coat and eye colour could be caused by a novel dilution of black (if B is
present) or by some other mutation (if B is absent). All of the cats share a common ancestor.
Their genotype (genetic makeup) shows they should be solid black but their phenotype
(visual appearance) is chocolate. This indicates a diluted-colour but the cats do not have the
dilution gene (d/d) at the D locus. In any case, “d” causes blue dilution i.e. black to grey. “d”
is one of the three genes involved in melanosome transfer and translocation. The unexplained
“Ukraine chocolate” seems due to a gene for which there is no test (at least in the cat).
Possible candidates are the other two melanosome transfer and translocation genes: Myosin
Va (MYO5A) and RAB27A. Genes involved in the synthesis of eumelanin other than
TYRP1, for example, TYRP2, are also possibilities. The other known dilutions in the cat are
the extinct Barrington Brown cats (none of which were bred outside of a laboratory colony)
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