Calicos

Does anyone know why all calicos are females? http://PetoftheDay.com/talk/confused.gif A book told me this, but is it true?

Calico cats are almost always female. This is because the gene that codes for coloration is found on the X chromosome. This "color gene" will code for a specific color such as black, orange, etc.

Each individual receives an X chromosome from its mother. It receives a Y (male) or X (female) chromosome from its father. Female kittens, then, have 2 X chromosomes and males have a Y and an X.

A cat must have 2 X chromosomes for it to be calico. It takes 2 X chromosomes to be female; and it takes 2 X chromosomes each carrying a gene that codes for a different color for the cat to be calico. Another chromosome (not the X or the Y) codes for white.

As the early embryo develops, some cells turn on one X chromosome, and some use the coding from the other. Let's say Cell A turns on the X chromosome whose "color gene" codes for orange. As cell A divides all its daughter cells will also code for orange. This results in a patch of orange, since the daughter cells remain in a group. Another cell, cell B, turns on the other X chromosome which happens to have the code for black. It's group of daughter cells will result in a patch of black. Because the early embryonic cells randomly turn on one X chromosome or the other, we get these multiple patches of color .

There are rare instances when a male kitten could have 2 X chromosomes and one Y chromosome. He then could be a calico if each of the X chromosomes has a "color gene" which codes for a different color.

Thats weird! are there any other breeds that are like this? http://PetoftheDay.com/talk/confused.gif

A coworker of mine has a male calico that when he took it to the vet and humane soc they both said "Let us put it out of its misery. Its not right" Well he took it home and I believe it is about 4 years old, tho he doesn't think it will live much longer. He said honestly it is brain damaged.

Yes, when the XXY occurs in humans the result is often a miscarriage or mental retardation with other birth defects.