About animals

Golden colors of cats and their genetic basis

Pin
Send
Share
Send



The genetic basis of gold colors

The first and main sign of color: from 1/2 (golden tabby) to 2/3 (golden shaded) or 7/8 (chinchilla) of each outer and integumentary hair, painted in a light or bright apricot warm tone. The shades of this tone on different parts of the cat's body can be different, but in no case should they turn into dull, grayish tones. The most common (not to say, nice) addition to the color of gold and shaded tabby is the residual ticking stripes on the painted dark part of the outer hairs, which either “smudges” the picture (in tabby) or gives a sloppy appearance of color (in shaded). This drawback is so widespread that it is considered almost as the norm <"the bug described in the dock is called a feature": -)>.
Very often color variations of cats are found, intermediate between gold and ordinary black tabby: the remaining hair of such animals is dyed in “gold”, but the undercoat is gray. Usually, the eyes of these individuals do not reach the emerald green color, characteristic of golden colors.
Among the golden cats with a picture (tabby), another variation is observed gold colorwhen both the undercoat is gold and the background of the spine is highly gilded, but the integumentary hairs in the figure are darkened almost to the roots. By the way, cats of this type never have ticking stripes in the picture, and the actual “gold” is an intense, almost copper color. Unfortunately, there are very few (?) Such animals so far.
Thus, among the golden colors you can select at least three different types, as well as all options for the transition between them.
For the first time, litter of golden chinchilla cats was received from silver chinchillas - parents. Such cases are not uncommon today. A new spectacular color immediately interested breeders, and for the first years of its existence, golden chinchillas were bred along with silver ones. Since then, two prejudices have been rooted: firstly, only Persians are golden, except for chinchillas or shaded (but not tabby!), And secondly, the golden color is determined by the presence of the same half-dominant inhibitor gene Iwhich provides the silver colors of chinchillas, shaded, silver tabby and smoky cats. Homozygotes according to the recessive allele of the same gene - ii - able to give only ordinary black tabby or monophonic individuals. It was believed that according to the mechanism of action of the gene I is an inhibitor of both eumelanin and pheomelanin. Thus, the hairs, with the exception of the most recently grown part - the tip, remain unpainted (white) under the action of the inhibitor gene. However, the work of only one gene, at least half dominant, of all color variations obtained in the silver-gold gamut, could not be explained. Therefore, geneticists-breeders put forward an idea about the genes of Rufism - that is, a group of genes that provide additional synthesis of the yellow pigment - pheomelanin. But this too vague assumption was not made satisfactory.
Moreover, after the Persian gold chinchillas, gold European short-haired, golden Siberian gold began to be found rapidly, not only shaded, but also cats with a picture. (Golden British cats, apparently, were not "discovered", but "made" with a mixture of the corresponding Persian cats). The search for the genes responsible for such a seductive color was continued.
Researchers first of all drew attention to the "Babylonian series", that is, the similarities in mutations of colors in different groups of animals. For example, Siamese cats, and Himalayan rabbits, and mouse acromelanists - they all have a color that is equally identifiable genetically. According to this law of parallelism, the dominant gene of the “wide band” - “wide band” - was nominated for the role of candidates for the genes of the golden color Wb -, found in some rodents. Under the action of this gene, a wide yellow stripe is formed at the base of the hair, and the animal acquires a zloty color. In the case of the action of the normal gene allele Wb it turns out the usual black tabby, but if you add an inhibitor gene to this genetic background, then a silver tabby is formed. When are the alleles I and Wb concentrated in one body, silver or shaded chinchillas are formed.
Another hypothesis, also based on color parallelism, is that cats have the “golden agouti” gene (a genetic symbol Ay), typical for dogs and mice. In most mammals that have been well studied genetically, the agouti complex is represented not only by two alleles, that is, gene variants known in cats (A - agouti and a - neaguchi), but a whole series of alleles. The so-called "sable" color of dogs, for example, is associated precisely with the action of the "golden agouti" allele and consists in yellow hair coloring (except for their dark tips). Based on the assumption that the same gene is present in cats, further considerations on the formation of a silver-gold color series will turn out to be similar to those described above, with the difference that the place is a hypothetical recessive wb will occupy the usual agouti factor A. We can conclude that at present, the most widespread theories of golden and silver colors, that is, based on two separate loci (or genetic complexes), are most common.

To get acquainted with one of the last theories of inheritance of gold and silver colors, based on the interaction of two independent genes against agouti or non-agouti mutation, we recall some features of the dilution of not only these, but also the so-called smoky and simple colors. They are as follows.
1. When crossing golden tabby or shaded cats, silver offspring do not appear, while the appearance of golden shaded when crossing silver chinchillas is a fairly common case.
2. Silver cats with a picture when crossing can give golden offspring only if the silver parents are not of high enough quality - there is a yellow tick in the picture, yellow overgrown flowers on the muzzle and other.
3. In the case of inbred breeding (crossbreeding) of cats with a pronounced golden color, golden descendants are born (sometimes clarified ones are cleaved).
4. During the unrelated crossings of golden cats, as well as when crossing them with silver, kittens with gray and brown undercoats are often seen among golden descendants, and among gray ones with yellowish ticking along the hairs and yellow above.
5. When crossing golden cats with black tabbies, all offspring or at least half of them are ordinary black tabbies, but descendants of intermediate colors are also found, moreover, in such individuals the undercoat is usually gray, and the “gold” is noticeable only on the outer hairs.
6. With unrelated crosses of smoky cats between themselves or with monophonic ones, descendants with a light gray, “cold” undercoat often appear.
7. On the other hand, among monochromatic cats, it is not uncommon to see individuals with a warm reddish tint on the coat and a tone of undercoat.

It remains to be assumed that the genes responsible for the silver color (melanin inhibitors, and, first of all, its yellow modification - pheomelanin), act independently of the gold color genes - eumelanin inhibitors, black pigment (the fact that the gold color gene is also an inhibitor , indicates the correlation of color with green undersighted eyes). In a recent paper (Cat Fancy magazine, 1995), these genes were named Bleacher and Eraser, respectively (unofficial names!). Each of these genes must be represented by at least two alleles, acting naturally on agouti or non-agouti background.
It is conventionally accepted that in the process of determining the color according to this scheme, all participating genes have the same genetic activity. In reality, of course, the dominance-recessivity ratios are not kept so strict, and the appearance of genes varies over a fairly wide range. The proof of this is the often noted intermediate color forms.

The interaction of these inhibitor genes is easier to illustrate with a table.

In addition, it is known that the degree of manifestation of a gene often depends on its dose, that is, the number of copies. For example, a gray-haired homozygous cat will have a more pronounced "silver" than a heterozygous one. In this case, one should take into account the frequent ability of genes to double, increasing their copy number as a result of mutations. Naturally, the desired color combinations are immediately fixed by the breeders, and in this way the number of copies of the gene in the population or nursery increases. As for the activity of the modifier genes of Rufism, their role is now great in the degree of intensity of the yellow pigment - from pale golden to bright copper. It is likely that their effect is associated either with the intensity of the synthesis of pheomelanin, or with the degree of its concentration in the hair follicles. These genes do not have an independent genetic symbol and exist, so to speak, “on bird rights”.
The scheme presented above cannot, of course, answer all questions of the formation of gold, silver and smoky colors. Why, for example, is there such a clear correlation between ticking the spine and the golden color of the hair base? It is possible that the components of the agouti complex play for these colors not only the static role of the genetic background, but are also directly involved in the formation of a golden (i.e. devoid of eumelanin) coat tone, i.e., in addition to the two allelic states of the agouti gene (A and a) there are other representatives of this genetic series, similar to the yellow agouti allele described above. The manifestation of the eu and pheomelanin inhibitor genes when exposed to other agouti alleles can produce the same, as yet unexplained effects of gold colors.
The breeders of these complex colors can be recommended as follows: for stability, keep moderately inbred (inbreeding 2-3b 2-4) mating animals in which the type of gold or silver color is the same, with the exception of the peculiarities of ruffism. Of course, to the extent reasonable, you should not "improve" the clogging ticking color or gray undercoat, and if you try to fix it, then only by pairing it with an individual that currently has a minimum of such shortcomings. However, any too long inbreeding leads to loss of progress in the breed. Therefore, when selecting unrelated pairs, it makes sense again to pay attention to a similar type of “gold” among the alleged parents.
But the final resolution of the problems of gold colors can, of course, be given by rather risky experimental mating. And the answer to the questions of the inheritance of "gold" can be found only under the condition of careful recording of the results obtained in several international associations.

Re: Shustrova. The genetic basis of golden colors

Provinces February 16, 2010 5:54 PM

For the first time, golden cat litter - chinchillas was received from silver chinchillas-parents. Such cases are not uncommon today. A new spectacular color immediately interested breeders, and for the first years of its existence, golden chinchillas were bred along with silver ones. Since then, two prejudices have taken root: firstly, only Persians are golden, just chinchillas or shaded ones (but not tabby!), And secondly, the golden color is determined by the presence of the same half-dominant inhibitor gene I, which chinchillas, shaded, silver tabby and smoky cats. Homozygotes, according to the recessive allele of the same gene — ii — are capable of producing only ordinary black tabby or monophonic individuals. It was believed that according to the mechanism of action, gene I is an inhibitor of both eumelanin and pheomelanin. Thus, the hairs, with the exception of the most recently grown part - the tip, remain unpainted (white) under the action of the inhibitor gene. However, the work of only one gene, at least half dominant, of all color variations obtained in the silver-gold gamut, could not be explained. Therefore, geneticists-breeders put forward an idea about the genes of Rufism - that is, a group of genes that provide additional synthesis of the yellow pigment - pheomelanin. But this too vague assumption was not made satisfactory.

Moreover, after the Persian gold chinchillas, gold European short-haired, golden Siberian gold began to be found rapidly, not only shaded, but also cats with a picture. (Golden British cats, apparently, were not "discovered", but "made" with a mixture of the corresponding Persian cats). The search for the genes responsible for such a seductive color was continued.

Researchers first of all drew attention to the "Babylonian series", that is, the similarities in mutations of colors in different groups of animals. For example, Siamese cats, and Himalayan rabbits, and mouse acromelanists - they all have a color that is equally identifiable genetically. According to this law of parallelism, the dominant gene of the “wide band” - “wide band” - Wb, found in some rodents, was nominated for the role of candidates for the genes of the golden color. Under the action of this gene, a wide yellow stripe is formed at the base of the hair, and the animal acquires a zloty color. In the case of the action of the normal allele of the Wb gene, an ordinary black tabby is obtained, if an inhibitor gene is added to this genetic background, then a silver tabby is formed. When the alleles I and Wb are concentrated in one organism, silver-colored or shaded chinchillas are formed.

Pin
Send
Share
Send