Many people are surprised to hear that the vast majority of calico cats
are female. Why is this? Is it possible for a calico cat to ever be
male? Learn about the genetics of coat color in this feline FAQ.
First off, what is a
calico cat? A calico cat is not a breed of cat, it is a color pattern. To be called "calico", three colors must be present: black,
white and orange.
Variations of these colors include gray, cream and ginger. A "true"
calico cat has large blocks of these three colors, a "tortoise shell" or
"tortie" cat has a mix of these three colors (blended/swirled together
more than distinct blocks of color).
Now that a calico cat has been defined as a cat with three colors, the
question is: why are they nearly always female? The answer is in
genetics. Coat color in cats is a
sex-linked trait, a physical
characteristic (coat color) related to gender. Female animals have two X
chromosomes (XX), males have one X chromosome and one Y chromosome
(XY). The genetic coding for displaying black or orange color is found
on the X chromosome. The coding for white is a completely separate gene.
Since females have two X chromosomes, they are able to "display" two
colors (orange and black, or variations thereof) and white; creating the
3-color calico mix. Since males have only one X chromosome, they can
only be orange OR black. It is more complicated than simply having the
color genes -- it is a complex process of dominant and non-dominate
genes interacting on the X chromosomes, but that is the basis for coat
color in calico cats. For those of you interested in the detailed coat
color genetics, please see the "Related Reading" articles at the bottom
of this FAQ.
Can a calico cat
ever be male? Yes, in rare instances. In this
situation, the cat has two X chromosomes and one Y chromosome (XXY).
Cats with this chromosomal configuration are usually sterile (not able
to breed). This is similar to a condition in humans called Klinefelter's syndrome, or XXY Syndrome.
Interesting calico cat fact: on October 1, 2001, the calico cat became the official cat of the state of Maryland in the United States.