Orange Tabby Females//Calico Males
Found this on a website at http://www.westcoastcat.com/scratchins/orangecats.html:
Are All Orange Cats Male?
Are All Calico Cats Female?
Dear Tabby explains the Birds and Bees and how your Cat’s Colour is Determined
All cats have 19 pairs of chromosomes. These chromosomes carry genes passed down from a cat’s two parents, and these genes determine a cat’s physical appearance, innate intelligence, susceptibility to disease and so on. There’s a copy of all 19 pairs of chromosomes in every cell of a cat’s body.
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 a cat’s colour. In females, both sex chromosomes are X making girl kitties XX. Males are XY, the Y making them male. A kitten gets one chromosome from Mom and one from Dad. Moms only have X’s so the variable is given by the Dad, if he gives his X, the kitten is a girl, if he gives his Y, it is a boy.
The gene which makes a cat ginger (orange) is located on the X chromosome. The gene for ginger will override all other colours. Since males have only one X, they either are or aren’t ginger - no halfway about it. Girl 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 a Calico or 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 calico (or tortoiseshell) female cats outnumber males by at least 200 to 1, some stats go as high as 3,000 to 1. When a male tortie does appear, (a result of a mutation producing two X’s and one Y) he is invariable sterile and exhibits feminine behaviour such as nurturing nearby young.
Why do we have so many orange and white cats? Because white isn’t a colour but the absence of colour. The genes that cause the suppression of colour are stronger than the genes for any colour including the mighty orange. Since white isn’t a colour and is merely hiding the genes for colour, white cats often produce coloured kittens.
All this talk about birds and bees! - I’m taking a break and going hunting!