Cats
especially where swirled patterns, black feet on white socks and skunk stripes are concerned.
Some cat breeders believed there were flaws in the conventional melanocyte migration
theory. For example a breeder working with American Shorthairs has been crossing Van
pattern American Shorthairs to bicolour and spotted Van pattern cats since the mid 1990s. She
found that the melanocyte migration theory could not account for some of the spotted patterns
these breedings produced. Alternative theories from other white spotting genes and
mechanisms in other species (dogs, horse, pigs and goats) also could not account for what
was appearing in her cats, particularly with 60%, 70%, 80% and 90% white on a cat. The
terminology used differs from the Grades 1 - 9 of the cat fancy; 90% white with a lot of
random spots is referred to as Level 15. Selective breeding has isolated most of the white on
the cats to a single layer of white
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