calico cat genetics

Floyd Waddle fwaddle at CHI1.UNCFSU.EDU
Tue Jan 21 18:17:03 EST 1997

Steven Pirie-Shepherd (srps at wrote:

> 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.
> As I recall (but this may be wrong), the colour gene is on the x
> chromosome, and since females have have two of these per cell, one
> must
> close down or 'condense' into a barr body. This gives rise to a mosaic
> of
> colour on the animal as the condensing is random from cell to cell.
> Males
> dont have two X chromosome in genreal, so they dont have a barr body,
> so
> they dont have the mosacitiy..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..make sense? --
>The gene for orange is O.  Its allele for non-orange (black) is o.  
The gene locus is on the X chromosome.  A tortoiseshell cat inherits O 
from one parent and o from the other.  In any mammal with two X 
chromosomes, one X becomes a Barr body (named after Murray Barr who 
discovered it).  Most genes on that X are nonfunctional.  In the skin 
of a tortoiseshell cat, those hair cells containing a functional 
allele O produce orange hair.  Those containing functional allele o 
produce black hair.  These cells tend to be mixed together, often 
producing alternating bands of color down the back.  White patches is 
due to an autosomal gene.  I don't know if it is dominant to nonwhite, 
or recessive.  However, the gene tends to cause the functional O 
bearing cells and the functional o bearing cells to separate out into 
discrete patches.  Some cats are gray and cream instead of black and 
orange.  This is due to a dilution gene which is autosomal and 
recessive to full color.

A year or two ago, I had opportunity to buy a calico male - for $1000! 
 Calico males must have two X's to be calico, and they must have a Y 
chromosome to be male.  Which makes them equivalent to Kleinfelter 
humans, and probably sterile.

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