Tortoise shells and ginger cats

[giraffe_02]

Why is is that tortoise shells are always female?

Why are ginger cats generally tom cats?

[drgnrdr]

It has something to with genetics/chromosomes or something..maybe a scientist can explain it...something about when orange XX is present it's male but when it's got black with the orange it changes the XX to XXY,,that's why most calico and Torties are female,,,if they do happen to get a male most of the time they are sterile, but if you get a male calico that can reproduce that is a rare kitty...maybe someone can explain it better...

[honeyboo]

Hi giraffe we have a ginger female called honey, she is 5 years old and loves catching birds. xXx

[janeo]

From Wikipedia: For a cat to be calico, it must simultaneously express both of the alleles, O and o, which are two versions of the same gene, located at the same location on the X chromosome. Males normally cannot do this: they can have only one allele, as they have only one X chromosome. Over 90% of tortoiseshell cats are females. Occasionally a male calico is born. These may have Klinefelter's syndrome, carrying an extra X chromosome, and will almost always be sterile or they may be a chimera resulting from the fusion of two differently coloured embryos.