Whether the truth that three-colored CATS are not?
the Nature does not cease to surprise mankind with the riddles. Why caterpillar “ tries on “ the cocoon, a chameleon changes coloring, and bees build the “ state “?, It seems, these phenomena are studied and scientifically explained long ago, but not everyone knows the reasons which are their cornerstone.
Genetics, according to many, at all a dark, an impassable jungle of science. All of us learned gradually that there are genes which develop in some surprising sequence, form unique and almost predictable combinations just as it is possible to make jewelry original and unlike at each other of different types of beads. It turns out that the general mechanism of inheritance is approximately familiar to us, and its narrower aspects, subtleties and cunnings are little-known. For example, you for certain had to hear that three-colored cats in the nature do not exist. What is the cornerstone of this fact? How to explain such whims of madam Genetika?
“ Before starting discussion, we will agree about terms “ - Yu. M. Lotman said. So let`s note at once that under the household name “ three-colored cat “ let`s mean a cat (but not a cat) a tortoise color, i.e. the color combining black and red (red), or black, red and white.
Widely famous statement about nonexistent tortoise cats is truthful only on a half. Such individuals nevertheless are born, though is extremely rare. In the majority they are sterile, that is possibilities of a reproduction are deprived.
The matter is that genes of basic colors of cats - black and red, are located in the same locus (the fixed place of a gene within a chromosome) on X - a chromosome which individuals of both floors have. The cat having a set XX can be red, black or tortoise (that is having both red, and black). Kot, the owner of HU, can have either a black, or red color. Schematically it looks so:
XX - a cat (two X - chromosomes, possible combinations: red, black, tortoise);
XY - a cat (one X - a chromosome, possible combinations: red, black).
We will assume that the gene of a red color is designated by a Latin letter O, and a gene of black - B, and we will represent one of options of inheritance of a tortoise color:
Black cat (XB XB) + red cat (XO Y) = 50% of tortoise cats (XB XO), 50% of black cats (XB Y).
It turned out that male kittens “ took “ a color at mother. The same situation is observed also in a case with posterity from " vapors; red cat and black cat “: the birth of tortoise kitties and red cats is possible. Arises here what sophisticated conclusion: the genes localized in X - a chromosome and not having an opportunity “ to be fixed “ in At - a chromosome, are transferred from mother to the son.
The Chinese popular wisdom says: if in a day you did not learn anything new, then day is lived in vain. I Hope, the “ today “ you did not spend for nothing?