I am not a cat lover, so I don't know if this is true, but I heard on TV today that all Calico cats are female. How is that possible?
A cat's fur color is determened by a gene on the X gender chromasome. The Y gender chromasome has no color genes on it. A Calico pattern is expressed by a pair of Dominant fur color genes: Black fur gene and an Orange fur gene. Since only the X chrmoasome carries the fur color genes, a cat would need an X gender chromasome with a black gene and and X gender chromasome with an orange gene. Thus, a male kitten born to a female calico can be either orange or black. A female born to a calico will depend on what color gene is donated from the father cat.
However, there have been rare reports of male calicos, only because the kitten contains an extra X chromasome making it XXY. In all mammals that have this genetic gender pattern, they are always sterile.
Wikipedia article on Calicos
I'm not sure if there's any analogue in human traits to something to can be co-dominant in women, and men rarely express. I do know thta co-dominant genes are common in humans as well. Anyone carrying a green eye gene and a brown eye gene will express both and have hazel eyes. The eye coloer gene, though, is not carried on the gender chromasomes--much less just the X's.
