Have you ever wondered how girls and boys are born? What determines the sex of babies? Next, let's get all these doubts out of your head. Come on?
In the human species, there are males and females, so we are considered dioic. Men and women differ thanks to the sex chromosomes. Each individual has 46 chromosomes, which are chains of DNA associated with proteins. Two of these chromosomes correspond to the sex pair, which is what determines sex.
In women, the sex pair chromosomes are equal and represented by XX. Men, on the other hand, have an X sex chromosome and another that is called a Y, so they are XY.
We know that, for fertilization to occur, a male and a female gamete are needed. The male gamete is the sperm, while the female is the egg. Each of these gametes has only half the chromosomes of the human species, so each egg and sperm have only one sex chromosome.
If the female is XX, all female gametes have only one sex chromosome X. Man, on the other hand, has X gametes and Y gametes. Let's assume that an egg has been fertilized by an X sperm, we will have a baby with sex pair XX, and hence the couple will have a girl.
If the Y sperm fertilizes the egg, will we have a girl or a boy? The answer is in the text below.
In the picture above, we have an egg about to be fertilized by a Y sperm. In this case, the baby will be XY, that is, it will be a boy. We realized then that who determines the sex is the sperm, therefore, the man. In genetics, we consider that there is an equal probability of being born girls or boys.
Curiosity: It is important to inform that sometimes, after fertilization, we find individuals with a lack or excess of sex chromosomes. When that happens, we have so-called sexual aberrations. As an example, we can mention Turner Syndrome, where the female individual has only one X chromosome. In addition to this syndrome, we have the Klinefelter syndrome, in which individuals are XXY and, because they have the Y chromosome, they are male.
By Ma. Vanessa dos Santos
