What are tortoiseshell and calico cats ?

[amoore]

I found this neat article in a little paperback book and wanted to share this with you . The book is called "Why do pets do that ?

A tortoiseshell cat is one whose fur is a mottled black and orange color . A calico cat is black and orange with patches of white . The odd fact about both these types of cat is they are almost always female. Male calico and tortoiseshell cats are rare . Only one in every 3,000 calico cats that lives past kittenhood is a male .
The explanation for this strange occurrence comes from genetics . In the cells of all animals are threadlike structures called chromosomes. Carried on the chromosomes are tiny coded messages known as genes . An animal's genes determine almost everything about it - whether it is male or female , what color its eyes ,skin and hair (or fur) are ,and a lot more
Chromosomes as we know, come in pairs. One of these pairs determines whether the animal will be male or female .Females have two x chromosomes ,while males have one x and one y. In cats the coded messages for black and orange coat color are carried on the x chromosome,but not the y.
A male cat, because he has only one x chromosome, can be either black or orange in color .In order to be black and orange, the cat needs two x chromosomes, one carrying the gene for black fur and one carrying the gene for orange fur Since any animal with two X chromosomes must be female, all black and orange cats are female.The extremely rare male calico or tortoiseshell cat has three sex chromosomes,two X and one Y.