In all dioecious species, that is, that have separate sexes, females have homologous sex chromosomes (XX), while males have a sex chromosome similar to females (X) and another typically male sex chromosome (Y), being then XX for females and XY for males.
The determination of sex takes place at the time of fertilization of the egg. In mammals, this determination is made through the sex chromosomes found in the male gametes, which are the sperm (XY), and in the female gamete, which is the egg (XX). We know that the human species has 46 chromosomes, where 23 of these chromosomes were donated by the mother (in the egg) and the others 23chromosomes were donated by the father (in the sperm). Because females have homologous chromosomes, that is, equal (XX), they will be able to donate to their children only the sex chromosome X, thus concluding that the mother does not have a significant role in sex determination. Therefore, we can say that sex determination is done by the father, as it can donate the sex chromosome
X, giving rise to a female baby, or the sex chromosome Y, giving rise to a male baby. In mammals, a gene is known to be present on the chromosome. Y, called SRY (sex-determining region Y), which determines the development of testicles and, consequently, the male gender in the baby.Determining the sex of children is the desire of the vast majority of parents, but as we saw in the previous paragraph, this determination depends on genetic factors. Some doctors, such as the American gynecologist and obstetrician Landrum B. Shettles, claim that it is possible to choose the baby's gender and to do so, just follow the method proposed by him to the letter, which can be found in the book "Likechoose your baby's gender". British scientists from the University of Exeter and Oxford published a study in which 740 women in their first pregnancy were observed. Based on these observations, they stated that the mothers' diet before conception and during the first weeks of pregnancy influenced the determination of the sex of their babies. Also according to the survey, women who had a more caloric diet were mothers of boys, while women who had a less caloric diet were mothers of girls.
Many theories have been developed and several studies have been and are still being carried out on this subject, which is very contested in the scientific world. This question will certainly be the target of many debates among experts. Therefore, the best thing to do is to wait until approximately the 13th week of pregnancy to know the baby's gender and always keep in mind the popular phrase: “that it comes with health, regardless of gender”.
By Paula Louredo
Graduated in Biology
Source: Brazil School - https://brasilescola.uol.com.br/biologia/determinacao-sexo-bebes.htm
