Reproduction and genetics

Cats are seasonally polyestrous, which means they may have many heat periods over the course of a year. A heat period lasts about 4 to 7 days if the female is bred; if she is not, the heat period lasts longer and recurs at regular intervals.

The male cat's penis has spines which point backwards. Upon removal of the penis, the spines rake the walls of the female's vagina. The female needs this stimulation for ovulation to begin. Because of this, females are rarely impregnated by the first male with which they mate. Furthermore, cats are superfecund; that is, a female may mate with more than one male when she is in heat, meaning different kittens in a litter may have different fathers.

The gestation period for cats is approximately 60 days. The size of a litter averages three to five kittens. Kittens are weaned at between six and seven weeks, and cats normally reach sexual maturity at six months (females) to seven months (males).

Completely white cats (not due to albinism, but white because of the dominant epistatic white (W) gene) with two blue eyes have a forty percent probability of being born deaf.

The deafness is an effect of the W gene. This gene produces a white coat because it completely masks any other color or pattern the cat has. Blue irises can result, and they are linked to deafness. Any cat that receives even one W from one parent may exhibit this. Blue eyes can also result from the form of albinism characteristic of the siamese breed; white cats from this genetic background, sometimes called Foreign whites or Oriental Shorthairs may not have a problem with deafness, but it can happen if the cat inherits the W gene. This also occurs with dogs if they have white coat and blue eyes, and in the case of dogs, it can be equally common for them to be born blind. However, blindness in cats has not found to be associated with the W gene. Often, blue eyes will lack a tapetum lucidum and thus will not reflect like colored cat eyes. This may diminish the cats' visual acuity, but the extent is not known. Humans with common albinism, white skin and blue eyes generally suffer from visual problems, but in Tietz syndrome they suffer from deafness.

Around 5% of all cats are completely white, of which 10%–20% are deaf. Very few survive in the wild because of all the hazards that they cannot avoid as easily as other cats would in the same situation. Many people believe that deaf white cats should not be used for breeding as it is not ethical to propagate such a disability, and instead deaf cats should be spayed or neutered to avoid passing the trait to their offspring. Some breeds however, such as the Turkish Angora are based on all white cats and produce a higher percentage of deaf cats as a results. It was not until recently that colored Turkish Angoras were allowed to be shown, making deafness an issue in that breed.