calico cat genetics

Scott Panzer stenor at
Tue Jan 21 19:26:29 EST 1997

In article <5bo1ju$2mb at> Steven Pirie-Shepherd,
srps at writes:
>Aeykay Ess (ditts at wrote:
>: HI Netters
>:  I have a couple of questions regarding calico cat genetics. I know this is not
>: the appropriate newsgroup for these queries, so I would appreciate if somebody
>: could direct me to such a newsgroup (or provide the answers).
>:  1) What is the genotype of calico cats and their parents.
>:  2) What is the origin of the white patches on these calico cats.

>[description of calicos being produced by X-inactivation snipped...]
>BUT it is possible to be XXY (Kleinfelter
>syndrome?). The superfluous X chromosome shuts down, resulting in a calcio
> basically all calico cats are female, unless they are male, in
>which case they must be kleinfelter cats.

Yes, calico and tortoishell patterning are due to X-inactivation
in a cat heterozygous for orange versus black alleles at the O
locus on the X chromosome.  Calico/torti males (Klinefelter equivalents)
are indeed rare, and are usually sterile.  They have no special
value as breeding cats.

The white coloring of part of the fur in calico cats is due to
alleles at the dominant white spotting locus, one of three
genetic loci causing white fur.  (The albino locus is a second).

The genotypes of the parents could be any combination that might
result in heterozygous female offspring.  Thus, orange male X black
female, black male X orange female, or any male X calico/torti female
could result in a calico or torti daughter.  These simple crosses
exclude consideration of other genetic factors that also affect
coat color.  For example, black, grey, chocolate, etc, and tabby
patterned versions of those are all considered "black" for our
purposes.  Orange and cream are both "orange" for the purposes
of determining whether the cat might be calico/torti.

rec.pets.cats has an extensive discussion of cat color genetics
in one of its FAQs

Scott Panzer                |  Department of Genetics, SHM I-310
stenor at            |  333 Cedar Street
panzer at |  New Haven, CT  06510
Phone: 203-785-2675    Fax: 203-785-6333   Alt Fax: 203-785-7227
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