Female is XX, male is XY, but why not have YY chromosome?

Anyone who learns organisms also knows the female chromosome is XX, male is XY. But why do X chromosomes be needed in men? Why is not YY?

You probably remember this legendary illustration in a biological textbook. Sex chromosome (chromosome) is a microscope, female is XX and male is XY.

Table of male chromosomes (left) and female (right).

What about NST YY? Are there any pairs of chromosomes, and if not, why? Basically, the answer is no. But to understand why, we will have to review a bit of chromosome knowledge in the human body.

Humans have 46 chromosomes, divided into pairs, meaning there are 23 pairs of chromosomes. In it, 22 pairs are normal chromosomes and the other one is called sex chromosomes. Chromosomes often determine basic traits such as height, hair color, skin color, rate of metabolism . while sex chromosomes determine the sex of the individual.

There are 2 types of sex chromosomes - X and Y. Women have 22 normal chromosomes and 2 X chromosomes, ie 22 + XX, and men have 22 normal chromosomes and 1 X, 1 Y, ie 22 + XY .

Sex determination mechanism.

Through this mechanism, we understand that X chromosomes will regulate "female", while Y is "male". But if so, why don't men carry YY pairs? Does carrying an X in the sex chromosome make " half-man " surname? Or does the YY pair make them "super-man"?

It is simply impossible

Chromosomes are genetic material in cells, but genes are actually things that contain genetic information, and each chromosome carries a different number of genes.

So the sex chromosome is not only responsible for sex determination, but also the genetic structures that assume hundreds of other roles. And the trouble is that the Y chromosome carries only a small number of genes - about 60-72 genes. X carries on it 800 to 900 genes.

Chromosomes are genetic material in cells, but genes are actually things that contain genetic information.

Over 300 million years of evolution, the number of genes has decreased by nearly 95% but the X chromosome still contains the number of genes enough to meet the survival requirements that a fetus must have. So, an individual who wants to survive requires at least one XST. If an organism is YY then it will not be a male, but super . bad.

The human body has a total of 20,000 genes, in the X chromosome gas, which accounts for approximately 5% of a sperm DNA. What about Y? Only 2%.

Besides that reason, what else?

X carries important genes that Y doesn't have. The first is the DMD gene - responsible for regulating Dystrophin. This is a protein that makes up skeletal muscle and heart muscle, which functions to strengthen and strengthen muscles, as well as protect them from injury. Dystrophin also has a small amount of neurons present, so it is extremely important.

Another key gene, CYBB , carries the code that regulates Cytochrome b-245 protein. This protein is essential for the enzyme NADPH oxidase - an integral part of the immune system.

Without these genes, a human being cannot live. So people must have X, or cannot exist.

There are people who suffer from XYY syndrome - one more Y Y.

There are also cases where a male mutation has an additional Y chromosome (XYY Syndrome - or "super-male" syndrome) . If you think XYY has more male characteristics: more muscular, more masculine, even more aggressive . then you're wrong.

XYY is a disease syndrome, so it is difficult for patients to develop normally. A person with chromosome XYY will in fact have more female-like characteristics, weaker muscles, reduced intelligence, and slower development.