Lately cat-fancies have begun to show a high interest to rare colorings, in particular to chocolate and lilac colored Himalayans - chocolate-point and lilac-point. As a result a supply is appearing on a cat market. Above all we wish to call to caution. First, multiple cases of false chocolates and lilacs have been detected - these are pale-colored specimen of seal-points and blue-points correspondingly. As since they don't carry "chocolate" gene they can't give chocolate and lilac offspring. Therefore to judge about the truth of a chocolate or lilac one should look at the attested pedigree. Second, some carriers of a "chocolate" gene that doesn't appear to be true homozygous chocolates and lilacs often have intermediate coloring. It's a hard task to distinguish such carriers - a seal-point from a chocolate-point and a blue-point from a lilac-point, especially in their young age. Only if both parents have chocolate or lilac coloring, one is able to guarantee that the kitten is a true chocolate or lilac.
IT should be noted that American system of kitten registration, exhibitions and refereeing is based on an absolute confidence to holders, and false chocolate or lilac may be estimated as true chocolate or lilac, as since referees reserve that coloring class, into which an animal was recorded while entering exhibition. Thus the estimate of an American ring (CFA, for instance) is not at all a confirmation of coloring verity.
"Chocolate" gene carriers are remarkable for a plenty of mistakes of this kind. Remember: a pair of "chocolate" genes (bb) - one from father and another from mother define a chocolate color when in a seal-point genotype (aabbcscsDD or aabbcscsDd) and define a lilac color (lilac-point) when in a blue-point genotype (aabbcscsdd). No special "lilac" gene exists. When only single unpaired "chocolate" gene (Bb) is presented in genotype, that is it passed from one of parents, then a kitten will be only a "chocolate carrier": its' phenotype stays seal-point or blue-point, and gene b is not displayed (recessive, or latent gene).
Some times a kitten is declared to have a chocolate or even a lilac "blood" on account of the fact that it has a chocolate or lilac ancestor in some generation. The notion "blood" in terms of heredity is outdated and erroneous and had existed among selectionists till the rules of genetics were discovered at the beginning of the present century. In fact the heredity is determined not by a "bloodwise" continuous substance that is diluted through generations but always remains in a diluted state but by discrete units -genes. Certain gene may be passed into an offspring from its' parent, and if not, "blood" is nothing to do.
In what case one may speak certainly about "chocolate" gene carriers in posterity?
1. In fact, all kittens in litter will certainly, on 100%, be the "chocolate" gene carriers in a single case: if one of parents is truly homozygous chocolate or lilac and another is not and not even a carrier.
2. If one of parents is true chocolate or lilac and another is a carrier of a "chocolate" gene, then a half of litter (on average of many litters) will be chocolates or lilacs and another half will represent true carriers.
3. On the contrary, never a chocolate or a lilac can originate as a result of mating of "chocolate" gene carrier and non-carrier. In this case one half of litter will be ordinary seal-points or blue-points and another will consist of carriers. Till they grow up and be exposed to a testing mating it is impossible to distinguish carriers from non-carriers: if chocolates and lilacs will be born then ex-kitten was a carrier, if not - then not.
4. Mating of a pair of "chocolate" gene carriers results in an especially difficult situation: statistically, if the sample is large enough (and by no means in each litter), half of it will demonstrate "chocolate" gene carriers, a quarter will consist of true (homozygous) chocolates and lilacs and another quarter - of non-carriers, ordinary seal-points or blue-points. Again, to separate carriers from non-carriers in the litter one should wait for animals' puberty and carry out a test mating.
In that way guaranteed "chocolate" gene carriers are of high value. Namely they appear to be the base of breeding of chocolates and lilacs of high quality. What is then the strategy of such breeding in the light of all foresaid heredity laws? One can see that two main ways of using of "chocolate" gene carriers exist.
1. The most effective way is mating of a carrier with a homozygous chocolate or a lilac. This way is best to bring about when female carriers are mated to a good cat sire - true chocolate or lilac. In this case, as it was mentioned, on average one half of litter will be homozygous by a "chocolate" gene that is will be true chocolates or lilacs.
2. Less effective but simpler way is to breed two carriers. More often these are a brother and a sister. By this strategy only a quarter of litter will have a chocolate or lilac coloring. And this means that on average one kitten per litter appears to have of a desired color, and in may happen that in given, concrete litter there won't occur any (but one may be lucky to get more that one kitten with a desired color!). Nevertheless, insistence and patience will help reach the target, and after awhile (probably after long time) one will succeed in getting a beautiful chocolate or lilac kitten of exhibiting quality.
Marnen Aslanyan, doctor of Biology Sciences, Professor of MSU department of genetic and selection
Alexander Spirin, doctor Of Biology Sciences, professor of MSU department of molecular biology
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).