Health Experience Notes
In the development of modern biology, we have gradually revealed the mystery of human reproduction. After the primary spermatocytes undergo meiolysis**, two types of sperm are formed—sperm with an X chromosome and sperm with a Y chromosome. Whereas, females produce eggs that contain only the X chromosome. This biological property provides the basis for our understanding of gender determination.
The eggs are passively fertilized, and they swim around the uterus waiting for the arrival of sperm. The sperm that first finds the egg will combine with the egg to form a fertilized egg. If the sperm containing the X chromosome is combined, then the sex of the zygote is female, and if the sperm containing the Y chromosome is combined, then the sex of the zygote is male.
It is important to note that it is not the mother who determines the sex of a child, but the father. The eggs produced by the mother do not determine the sex of the child. Therefore, whether to have a boy or a girl is ultimately up to the father.
Normally, a primary spermatocyte undergoes two meioses** to produce four spermatozoa, two of which contain the X chromosome and two of which contain the Y chromosome. The ratio of these two types of sperm is 1:1. This means that for every pregnancy, the probability of having a boy and a girl is the same.
However, in everyday life, it is easy to find that some families have children who are almost all boys or all girls. For example, there may be a family with four boys and one girl, or four girls and one boy. This phenomenon makes us wonder: is it easier for some parents to have boys and others to have girls?
In fact, it is not determined by the parents, but by biological randomness. Every pregnancy is a random process, and the probability of having a boy and a girl is always 1:1. Families with extreme sex ratios only happen to have a higher number of children of one sex in multiple pregnancies.
In summary, the sex of the child is determined by the father, and the probability of having a boy and a girl is equal under normal circumstances. Those families with extreme sex ratios are only due to randomness in multiple pregnancies.