Sexual activity of men depends on the "female" X chromosome
Last reviewed: 16.10.2021
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Sexual behavior of the stronger sex does not necessarily depend on hormones: perhaps some areas of the "female" X chromosome directly determine the sexual activity of men, bypassing the hormonal mechanisms.
The difference between a man and a woman is determined by the hormonal balance - this is a well-known fact. If the child got a male sex, then from the fourth week of pregnancy the fetus will be treated with testosterone. The level of hormones is determined by sex chromosomes, but how much do these chromosomes affect behavior? The answer would seem to be obvious: male hormones form and male behavior. But scientists from the University of Virginia (USA) came to the conclusion that in this issue, not everything is determined by hormones.
In order to clarify the role of sex chromosomes in the formation of behavior, scientists transferred the genes determining the male gender from the Y-chromosome to the usual, non-sexual one. Such a mutation made it possible to obtain males with two X-chromosomes. In the XX-males, the production of testosterone was the same as that of the usual XY, but surprisingly, their behavior was more "courageous": they were more actively looking for females and more often had sex. From which the researchers concluded that male behavior does not depend on the level of testosterone and is most likely controlled by the X chromosome.
To confirm this, scientists compared ordinary XY-males to XXY-males. Although in men the extra X chromosome leads to the development of Klinefelter's syndrome, in mice such males also exhibited intense "male" behavior. It should be emphasized that in this case, researchers focus on behavior, and not on the appearance and physiology of animals. How these data correlate with physiology and human behavior, time will tell. However, it is worth mentioning that XXY-men show more sexual activity than men with a usual set of sex chromosomes.
There is a hypothesis according to which the X chromosome in men displays moderate activity: according to some estimates, about one-quarter of genes work in the male body. In this case, it is easy to assume that these genes are responsible for sexual behavior in men, and an additional copy of the X chromosome makes this behavior even more pronounced, although he has to contend with a not very suitable hormonal background. But for the final confirmation of this theory, it is necessary, of course, to determine in the X chromosome a site that, bypassing hormones, affects sexual activity.