why are most calico cats female

Most calico cats are female because the genes that determine their distinctive black and orange patches are located on the X chromosome. Female cats have two X chromosomes (XX), so they can inherit one gene for black fur and one for orange fur, resulting in the calico pattern. Male cats typically have one X and one Y chromosome (XY), so they can only inherit either black or orange, but not both. Rare male calico cats exist when a male cat has an extra X chromosome (XXY), a condition called Klinefelter's syndrome. These males can show the calico pattern but are usually sterile and very rare, about 1 in 3,000 calicos. The white patches in calico cats are due to a different gene not located on the sex chromosomes and contribute to their distinctive tri- color coat appearance. Thus, the calico color pattern is linked to the genetics of the X chromosome and X-inactivation in females, making most calico cats female.