Re: Ginger females have you met one?
Don't know if this will work. It's from 'Notes and Queries' in The Guardian.
It's all X and Y again, as I suspected!
It has been my observation that in the cat world tortoiseshell (known in the US as "calico") cats are always female, while all ginger cats are male. Can anyone explain/confirm this ?
Chris Martin, Bridgeport, USA - As a cat lover myself I always considered the above assertion to be true. That is until one day, when I visited a cat protection league re-homing centre, and saw a female ginger cat suckling her litter of three (all ginger) kittens. In order to explain this we need to consider Kitty genetics. All cats have 19 pairs of chromosomes, and like humans, cats have one pair of sex chromosomes. These are the ones that make them male or female and they play an essential role in determining their colour. In females, both sex chromosomes are X making females XX. Males are XY, the Y making them male. The gene which makes a cat ginger is located on the X chromosome. The gene for mighty ginger will override all other colours. Since males have only one X, they either are or aren't ginger. Female cats have two X's in each cell. As far as the cells are concerned two X's is one too many, so each cell deactivates one of the X chromosomes in a fairly random fashion. Sometimes the ginger X will be left on producing a bit of orange fur and in some cells the ginger X will be turned off and the genes for black, brown or other colour fur will be produced. And there you have Tortoiseshell Cat. Since males only need to have the orange gene on one chromosome to become ginger, and females have to have it on two, ginger males outnumber females 3 to 1. To show both orange and another colour such as black or brown a cat has to have two different X chromosomes per cell. Therefore tortoiseshell female cats outnumber males by at least 200 to 1, although I suspect actual figures are much higher. When a male tortie does appear, (a result of a mutation producing two X?s and one Y) he is invariable sterile and may even exhibit feminine behaviour such as nurturing nearby young. So the answer to your question is that your observation is, as a rule of thumb, spot on as far as tortoiseshell's are concerned, although female gingers are fairly common.
Huw Rees, London UK
- All tortoiseshell and tortoiseshell and white (Calico) cats are female. But not all gingers are male, though most are. The reason is that in cats the colour gene is carried on the X chromosome. As females have two Xs they can express two colours in the coat, and if black is inherited from one parent and ginger (red) from the other, the result is a calico cat. The calico's brother, having only one X chromosome, would be either ginger or black, depending on the colour of the mother. I believe there was a case of an apparently male calico cat but it was found to have a mutation giving an XXY chromosome set-up, and was sterile. For a female to be ginger she would have to inherit red from both parents. This could happen if the father was ginger and the mother tortoiseshell for example. The white is inherited on a separate gene and is independent of the colour gene. It can appear on either sex and with any colour of coat. For some reason not understood it is usually found that in tortoiseshell and white cats the patches of black and ginger are larger and more distinct than in the plain tortoiseshell without white. A tabby pattern of stripes can also be inherited separately, resulting in a cat known as a "torby" (Tabby-tortoiseshell).
Susan Deal, Sheffield UK
- Calico cats are always female (or XXY males) as the mix of colour is generated by the fact that in each cell in the embryo, one of the X chromosomes is 'switched off'. This process is random, meaning that some groups of cells have the paternal X active and others have the maternal X active. In fact this process happens in all female mammals, but not all mammals carry skin/fur colour on the X chromosome so it isn't so apparent. Ginger cats can be male or female. The ginger colour is recessive and carried on the part of the X chromosome not matched by the Y. Thus, any male cat inheriting this from the mother will be ginger, whereas female offspring, inheriting a differnt colour allele from one parent are more likely to mask the ginger. Female ginger cats inherit the recessive ginger allele from both parents. (Colour blindness in humans works the same way)
Ann, Leicester UK
- Approximalty 99.5% of tortise shell cats are female. About 75% of ginger cats are male. It has been previously clearly stated how the calico and tortise shell cays come about, and why they are nearly always female. However, the Ginger cat mystery is still not clearly explained.
- There was more but it made the post too long
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