Teaching genetics and embrionologi, found that up to three months of fetal development, all embryos originally - girls. Why it happens?
Basic PACKAGE
Historically, that the basis of an unborn child is giving the female egg. It follows that the basic child's gender is always female: it is the female egg carries the X-chromosome.
Male sperm - the carrier Y-chromosome. And with the general biology lessons at school, we remember that the fusion of male and female gametes and contained in their "base set" of chromosomes formed the child's sex. Our kind of female there is the "default" - this is the base model. The embryo begins to develop, it is having female traits (and therefore men have nipples).
Further education floor goes under the "supervision" of parental hormones, which also determine the sex of the future will be a pipsqueak. If the male hormone will be dominant to begin the formation of the boy.
men are more difficult
Formation of a male fetus passes more complex way than embrion- "girl." When approximately 8 weeks of fetal Y-chromosome causes the body of the embryo to the production of testosterone, the brain of the child We have to rebuild: to get rid of the cells responsible for communication, care and breastfeeding, and "grow" sexual activity centers and aggression.
Relatively simple reproductive system of women is replaced by a more complex male fetus in the body, boy, new fabric - the testicles and prostate gland. Therefore, in order to grown man, embryonic cells need to share more often.
XY is more vulnerable
Scientists have identified the combination of XY-chromosome, which "provides a" male sex is more vulnerable than the XX-set. Why? It turns out that in the embryos of the girl, if one of the X-chromosome is damaged, ready kind of "alternate" that does not exist in the male fetus. In addition, the X-chromosome contains more useful genetic information for brain development, regeneration, so geneticists believe that the reason why boys often threatens autism.
Morris syndrome
It can happen and fail in the body - the so-called Morris syndrome - when the embryo does not respond to received male hormone and continues to evolve as a girl. The light appears the girl having a male character (for this reason, the participants of the Olympic Games are tested for genetic sex, in order to equalize the chances of all participants competitions). That's the story.
