Black and red

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

Genetics, in the opinion of many, and did a dark forest, impenetrable jungle of science. We all brand name viagra 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, and the more narrow aspects of it, subtlety and cunning little known. For example, you probably have heard that tri-color cats do not exist. What lies at the basis of this fact? How to explain such oddities Mrs. Genetics?

"Before venturing discussion, agree on terms", - said YM Lotman. So let's just note that, under the household name "tricolor cat" will mean a cat (not the cat), tortoiseshell color, ie, color, combining view of normal men red and black (red), or black, red and white.

Widely known fact about non-existent tortoiseshell cats is only half true. Indeed, such individuals still born, though extremely rare. Most of them are sterile, that is unable to continue the race.

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 a 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 both red and black). Cote same, the owner of HU may be either 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 the Latin letter O, and the gene black - B, and represent one of the options for succession tortoiseshell color:

Black cat (XB XB) + red cat (XO Y) = 50% tortoiseshell 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 applies in the case of the offspring from a pair of "red cat and a black cat": perhaps the birth of a tortoise cats and red seals. This suggests that's a tricky conclusion: genes, localized on the X chromosome and have no opportunity to "consolidate" in the Y-chromosome, passed from mother to son.

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