For those people with a cat, the article http://en.wikipedia.org/wiki/Cat_coat_genetics is interesting reading.
Extracts:
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Genes involved in albinism, dominant white, and white spotting
The temperature sensitive albino genotype cscs produces point coloration at body extremities
The “C” gene codes for the enzyme tyrosinase, the first step in pigment production. Its recessive alleles determine whether a cat is a complete albino (pink-eyed) or a temperature sensitive albino. The temperature sensitive albino genotypes are cbcb Burmese (sepia), cscs Siamese (pointed), and cbcs Tonkinese (mink). The cscs gene can turn a cat’s eyes blue due to a reduced number of melanocytes, affecting pigmentation of the eyes. If a cat has the dominant C allele, then the cat is non-albino and full pigment production occurs.
The white spotting or piebald spotting gene, S/s, has variable expression, so that an SS cat often has more extensive white patching than an Ss cat. It is this gene that creates the familiar white blaze across the face, a white bib, tuxedo pattern, or dappled paws.
The sex-linked red gene, O, determines whether there will be red variations to fur color. This gene is located on the X chromosome. In cats with red variants of fur tone, phaeomelanin (red pigment) completely replaces eumelanin (black or brown pigment).
For a cat to be tortoiseshell, calico, the cat must simultaneously express two alleles, O and o, which are located on the X chromosome. Males normally cannot do this. Approximately 1 in 3,000 calico/tortoiseshell cats are male, chimericism appears to be the most common mechanism.
One can deduce that a grey male cat with a white bib and paws, but showing no tabby pattern:
a) has the o variant of the orange gene on its only X chromosome (because the grey color corresponds to black, not orange)
b) has at least one S variant of the white Spotting gene (because it has the white bib and paws)
c) has two w alleles (because it expresses a fur color)
d) has the dominant B allele (because its fur color is a shade of black rather than brown)
e) has two d (dilute) alleles (because its fur is grey, rather than black).
Tabby cats (AA or Aa), normally have:
a) M on forehead.
b) Thin pencil lines on face.
c) Black “eyeliner” appearance and white or pale fur around eyeliner.
d) Pigmented lips and paws.
e) A pink nose outlined in darker pigment
f) Torso, leg, and tail banding.
Cat fur length is governed by the Long hair gene in which the dominant form, L, codes for short hair, and the recessive l codes for long hair.
