Well, from what we know, humans have 23 pair of chromosomes, with the X and the Y chromosome playing a very important role in determining the sex of a child. Genetically speaking, all females have XX chromosomes while all males have XY chromosome. So you can see that the Y chromosome is very important in determining the sex of a baby. However, the portion of the Y chromosome that is actually important for determining sex is the SRY region, whose transcription and translation further instigates other mechanisms to occur that give rise to primary and secondary male characteristics. This is the reason why some people have two X chromosomes but have phenotype akin to that of a male. It is mainly because during crossing over the two homologous pair (X and Y) ended up taking part in it (which does not usually happens with sex chromosomes) and the SRY region ended up in the X chromosome. Therefore, its transcription and translation opened doors for other mechanisms, like deterioration of the mullerian duct to occur and development of male characters. Furthermore, there are cases where a person has XXY and XO chromosomes. These are basically genetic disorders, with the latter occurring in females and the former occurring in males. In both the cases, the person suffering from these conditions are generally sterile. I have seen people bring these conditions up when talking about transgender people but I am not sure of the extend to which these genetic disorder cause such behavior. There are also cases of XXX females (Poly-X females). They are completely normal, usually tall and pretty looking(which is completely subjective). But as the number of X chromosome exceeds three, some mental problems like cognitive disorder may occur.
So to boil it all down, the Y chromosome (SRY region to be more specific), which always comes form the male parent, is very important in determining the sex of a baby in the case of mammals. The role is reversed in the case of birds and insects follow different route.
PLease mark as brainliest
