Heredity and Breeding - Cat Show

Basic mechanisms of heredity
Breeding for showing depends on the workings, be they calculated or accidental or plant contains structures called chromosomes. These look like microscopic string carries details of the design of some particular part of the body. Some genes are concerned with eye colour and so on. The genes are arranged in a fixed order along the length of the chromosome, so the chromosome contains a “blueprint” of the total make-up of an individual.

Domestic cats carry thirty-eight chromosomes arranged in pairs of nineteen. Eighteen if these pairs are virtually identical, but one pair differs slightly This is the pair that decides the kitten’s sex. Females carry a pair of so-called “XX” chromosomes, while males carry an “XY” pair. A kitten will inherit one of its mother’s X chromosomes plus either the X or Y from its father, and thus its own sex will be determined.

Each kitten in a litter inherits genes from both father and mother in equal amounts but they will be arranged in a slightly different order along the chromosome head chain. It is this new arrangement that gives each kitten its individuality.

Occasionally outside factors, such as X-rays, can alter the fundamental characters of genes, and the changes they induce are called “mutations”. Sometimes, thought very rarely, a gene mutation occurs spontaneously. Changes such as these result in the sudden popping up of new breeds, colours and types of cat.

Linked genes
Some genes tend to stick together and pass “arm in arm” from one generation to the next. These are “linked genes” and, where they are found on only one of the pair of chromosomes, are termed “sex-linked” genes. A good example of this in the cat is the fact that tortoiseshells are always female. A tortoiseshell coat is produced by a combination of genes linked to the female chromosome, and a male cannot therefore inherit it.

Dominant and recessive genes
Dominant genes are those which tend to get their own way, while recessive genes are shy and retiring types. When two colour-carrying genes meet in a newly fertilized egg it is the dominant one that dictates the eventual colour of the kitten that will be born. Tabby (agouti) coloured genes, for example, are dominant, whereas solid (non-agouti) genes are recessive.

Undesirable genetic effects
A dominant white gene frequently induces wasting away of the inner ear structures. This is why white cats, particularly ones with blue eyes, have a tendency to deafness.

The Manx gene carries the inherited deformity of tail-lessness. Where kittens inherit Manx genes from both parents they usually die before birth.

The Manx gene, which causes tail-lessness, is similar to the condition of spina bifida in humans. If Manx genes are passed on by both parents, the kittens die in the uterus. Manx therefore aren’t true-breeding cats. The fact that they survive at all means that they can only be carrying one Manx gene in each pair of chromosomes.

The squint of the Siamese is caused by an inherited fault in its vision.

The Siamese gene may produce a defect in the optic nerve connecting the eye to the brain. This results in reduced binocular vision and a degree of double vision which the cat tries to correct by squinting.

Extra toes are a genetic characteristics

Some other undesirable effects controlled by genes are hairlessness (sometimes allied to red genes), undescended testicles, badly positioned ear flaps, extra toes (polydactyly) and a cleft in the forefeet (splitfoot).

Cornish Rex (left) and Devon Rex (right)
Mimic genes: occasionally quite different genes can produce similar bodily effects. These are said to be “mimic” genes. There are two well-known feline mimic Rex genes – the Cornish and the Devon. These two breeds look similar but genetically they have developed separately.

A phenomenon known as masking occurs when some genes are so powerful that they swamp the characteristics produced by other genes. The best example of this is where the non-agouti gene masks the effects of the various tabby genes. This explains why a black cat with tabby genes usually has no tabby markings – the non-agouti gene has eliminated the agouti ticking of the hairs to produce a solid black appearance. Sometimes partial masking occurs, explaining why a faint tabby pattern is often seen in the coat of young, solid-coloured kittens.

A British Cream kitten showing faint tabby markings from a "masked" gene.

Selective breeding
The breeding of show cats has to operate within the labyrinth of miraculous natural processes that has just outlined. Little can be done yet by way of genetic engineering, although the day may come when we can actively make cats the way we want them. The breeder must select those characteristics that he wishes to promote, and enhance them by careful breeding plans. He can suppress unwanted features (crow-eyed Siamese have been quite successfully “bred-out”) and experiment by crossing cats of different body type, colour, hair length and so on.

Pedigree Birman kittens

Of course, to win prizes at the cat show, the end product of all this considered breeding must resemble the ideal standard currently in vogue for a particular breed.

Cat for showing
In cat shows, pedigree cats are judged against a scale of points for their particular breed. The maximum number of points is one hundred, with marks being deducted for features that do not match the breed standard. If your cat isn’t up to scratch for showing, then consider buying a good pedigree kitten. Register it with the governing body or, if it is already registered, notify the change of ownership. In order to breed cats for shows it is best to start with one or two female kittens, rather than to buy an entire male (stud). Remember, however, that if you are going in for a rare breed, suitable studs may be difficult to find.

* Always consult an experienced breeder and join a cat club before you begin.
* Wait until your kitten is one year old before starting to breed.
* Compare the pedigrees of various studs and select the one most suited to your queen. Your aim should be to improve on her characteristics.
* Go to cat shows in order to study the potential stud’s kittens and the judges opinions of them.

If you haven’t got a pedigree cat, don’t worry. There is a “Household Pet” class at many shows in which prizes go to the prettiest or most characterful individuals.