Sex and the kitty


For anyone who’ve decided you know your cat is a what-what-what, you may find youself wondering a bit more now and asking why-why-why. For example, why are torties and calicos girls, invariably? Here’s a very quickie primer from messybeast, with links to pages with more in-depth discussion:

QUICK FACTS

ARE GINGER CATS ALWAYS MALE?

No. This is a common misconception. Ginger cats can be either male or female although ginger females are less common.

The genetics of ginger is explained in more detail in Tortoiseshell and Tri-Colour Cats (ginger is caused by the same gene as tortoiseshell), but this is a short version for those wanting a quick answer.

The ginger gene changes black pigment into a reddish pigment. The ginger gene is carried on the X chromosome. A normal male cat has XY genetic makeup so he only needs to inherit one ginger gene for him to be a ginger cat. A normal female is XX genetic makeup so she must inherit two ginger genes to be a ginger cat. If she inherits only one ginger gene, she will be tortoiseshell with some ginger areas and some black/brown areas.

The ginger gene is called a sex-linked gene because it is carried on a sex chromosome.

Also, if you look closely, ginger cats have tabby markings though these may be faint or only visible on the face, tail and lower legs. They are also visible in the ginger areas of tortie cats. This is because the gene that turns off tabby to give solid colour cats does not work on the ginger colour.

ARE GINGER FEMALES RARE?

No. They are less common than ginger males, but they are not rare. It is possible to selectively breed ginger female cats by mating ginger males and ginger females together. They will have ginger offspring.

ARE GINGER FEMALES STERILE?

No. They are just as fertile as other female cats!

ARE TORTOISESHELL AND CALICO CATS ALWAYS FEMALE?

No. Though they aren’t very common, tortoiseshell and calico males occur more often than most people realise and more of them are fertile than people realise.

The genetics of tortoiseshell males is explained in more detail in Tortie Tomcats, but this is a short version for those wanting a quick answer.

WHAT CAUSES TORTIE AND CALICO TOMCATS?

The most common cause seems to be chimerism. Two embryos bump into each other in the womb and merge together. If one is black and the other is ginger and one or both are male the result may be a tortie tomcat (or calico tomcat if the embryos had white patches).

The next most common cause seems to be XXY genetic makeup (Klinefelter Syndrome). An embryo gets one X chromosome with the black gene, one X chromosome with the ginger gene and one Y chromosome that makes it male. This chromosomal abnormality used to be thought the most common cause, but recent research shows chimerism is probably more common.

The third cause is somatic mutation. A ginger male embryo devlopes black patch in the same way as some babies develop port wine stain birth marks.

ARE TORTIE AND CALICO MALES ALWAYS STERILE?

No. It depends on which of 3 conditions has caused their colouration.

Those with XXY makeup are infertile and often have other physical abnormalities due to having too many copies of some genes..

Those with chimerism are fertile but they can only pass on either the ginger colour or the black colour, but not both, to their offspring.

Those with somatic mutation are fertile because the black patches are just birthmarks.

ARE TORTIE AND CALICO TOMCATS VALUABLE?

No, but people who advertise them as “rare” would like you think so!

Because they are either sterile or they only pass on either ginger or black to their offspring, they are no more valuable than any other cat (value will also depend on what breed it is). Some superstitious people think they bring good luck.

For the nerdy scholarly, “Basic Genetics as Revealed by Cats” offers a very nice brief but thorough introduction with more details. It even covers the why and whereof of Tabbies.

Personally, throughout Areas 1 to 3, the kitties we meet else, and in Foster Mum’s cattery, we’ve only come across tortie females. Ginger kitties on the other hand, seem rather well-represented by both sexes, though males have a slight edge. As for calicos, it does seem females dominate the field too, and we’ve only come across one calico male, and a dilute with blue eyes at that.

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