The concept of selective breeding was first discovered in the mid 1800 by the Austrian monk by Johann Mendel. He put forth two “laws” that fell into obscurity until their rediscovery in the early 1900s.
Mendel’s first law stated that if two parents of pure strains are crossed and they differ in only one trait for which one has two dominant factors (his word for genes) and the other has two recessive factors, all the offspring of the first generation will display the dominant factor trait. For example, the crossing of a true breeding black coated parent and a true breeding blue coated parent will result in a black coated kitten, Black is dominant over blue.
The second law states that crossing of the offspring will then produce variety in that same trait. Some will look like each of the grandparents in terms of that trait and some will look like neither. Therefore, some of the next generation will have black coats, some blue coats and some will have other coloured coats.
We know today that all features of any cat or any living creature for that matter, are controlled by genes, which are situated on chromosomes. When fertilization takes place, the sperm cell from the male unites with the egg cell from the female and the chromosomes of the created offspring are arranged in pairs. Half of each pairs comes from the father, while the other half comes from the mother. Thus, the newly created animal is given its genetic programming, its features have been determined.
Breeders attempt to produce Kittens with top show potential by continuing the best features of the parents and improving on other features. They can concentrate entirely on the esthetic qualities, because the usefulness of the animal in terms of function need not be considered. Whereas breeders of other animals may also consider “abilities” or purpose of what the offspring is to be used for such as race horses, beef cattle, working dogs where appearance many not be the number one reason.
New Breeds and varieties are established in one of 3 ways.
Mutation-such Cat breeds as the Sphynx, American Wirehair, Cornish Rex and Devon Rex are examples. Mutations are impossible to predict, but when they occur, they are passed onto subsequent generations like any other gene.
Recombination of Mutant Genes-this generally gives us new color varieties rather than entirely new breeds. It is how breeders eventually developed a dozen varieties of the Burmese Cat.
Ongoing Selection of the Polygenes-also known as the quantitative genes, to produce the desired characteristic. No mutation is involved, only the selection for further breeding of the members from each new generation that best demonstrates the desired characteristics. The Siamese was a man-made process for many generations.
Mutation can explain the fact that kittens of domestic cats are born domestic. With most wild species, the domestication process must be repeated with each new generation. Another important term in breeding is “inbreeding”. This in itself, is neither good not bad. It is simply a process.
Breeders commonly use inbreeding to purify bloodlines, such as breeding the best to the best to get closer to that “ideal” cat. Inbred offspring resemble each other more with each new generation. But with inbreeding, caution must be exercised to ensure that no harmful recessive trait is brought out. For example in some animals, temperament, poor confirmation.
If a Cat Breeder wanted to obtain long haired kittens with point coloring, they would breed a “purebred” longhair ie. black and cross it with a pointed shorthair ie. Siamese. The genes for the black color and short hair are dominant and so all of the kittens will have these characteristics. However, all of the kittens will also have genes for point coloring and long hair. Than, if some of these kittens are crossed, the next generation could include cats with various permutations of the four characteristics (black/point/long haired/shorthaired), including some of the desired longhaired cats with the point coloring.
You will often hear the words “Homozygous” which means breeding true. Heterzygous is “mixed” or considered the “recessive” gene. As you first experiment with your breeding, you may note that some of your litters are consistent, others are not as they will contain both of the above dominant and recessive genes. However, as you continue to mate some of the selected offsprings, this is when “selective breeding” will bring out the desired feline offsprings.