Thursday, October 22, 2009

Is it true that the three-color CATS does not exists?

three  color cat
Nature never ceases to amaze mankind its riddles. Why caterpillar "trying on" a cocoon, a chameleon changes color, and the bees build their "state"? It seems to be these phenomena have long been studied and scientifically explained, but not everyone knows the reasons behind them.

Genetics, in the opinion of many, and there is a dark forest, impenetrable jungle of science. We all learned a little, that there are genes that are added to some amazing sequences form a unique and almost predictable combinations, just as different types of beads can produce original and delightfully different decorations. It turns out that a common mechanism of inheritance to us about the sign, but more narrow aspects of it, subtlety and cunning little known. For example, you probably have heard that three-colored cats in nature does not exist. What lies at the basis of this fact? How to explain such oddities Mrs. Genetics?

"Before contrive discussion, agree on terms", - said YM Lotman. So let's just note that a household name "tricolor cat" shall mean the cat (but not the cat), tortoiseshell color, ie color, which combines black and red (red), or black, red and white.

It is widely known statement of non-existent tortoise cats only half true. For such individuals still born, though very rarely. Most of them are sterile, that is deprived of the possibility of procreation.

The fact that genes are the basic colors of cats - black and red, are located in the same locus (fixed location of the gene within the chromosome) on the X chromosome, which have both sexes. The cat, having a set of XX can be red, black or tortoise-shell (ie, having a red and black). Cote same, the owner of HU, may have either a black or red color. Schematically it looks like this:

XX - female (two X chromosomes, the possible combinations: red, black, tortoiseshell);
XY - male (one X chromosome, the possible combinations: red, black).

Assume that the red color gene is denoted by Latin letter O, and the gene black - B, and depicted one of the options inheritance tortoiseshell color:

Black Cat (XB XB) + red male (XO Y) = 50% tortoise cats (XB XO), 50% of black cats (XB Y).

It turned out that the kittens are male "have" color of the mother. The same situation is observed in the case of the offspring from a pair of "red cat and a black cat": perhaps the birth tortoise cats and red seals. Here arises a tricky conclusion: genes, localized on the X chromosome and have no opportunity to "consolidate" in the Y-chromosome, passed from mother to son.

Chinese folk wisdom says: if one day you do not learn anything new, you lived through the day in vain. I hope your "today" you will not have wasted?

Anna Cat

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