feed home

How is the genetic determination of sex established in humans?

In the diploid genome of human beings there are 46 chromosomes, 44 of them are autosomes and two are sex chromosomes. The individual inherits one sex chromosome from each parent.

The human sex chromosomes are called X chromosome and Y chromosome. Individuals having two X chromosomes (44 + XX) are female. Individuals having one X chromosome and one Y chromosome (44 + XY) are male. (Individuals 44 + YY do not exist since the chromosome Y is exclusively from paternal lineage.)

What are the homologous and the heterologous portions of the human sex chromosomes?

Homologous portion is that in which there are genes having alleles in both Y and X sex chromosomes. The homologous portions are situated more in the central part of the sex chromosomes, near the centromere.

Heterologous portion is that whose genes do not have correspondent alleles in the other sex chromosome. These genes are located more in the peripheral regions of the arms of the Y and X chromosomes.

Concerning the sex chromosomes of the XY system which type of gamete do the male  and the female individuals respectively produce?

The individual of the male sex is XY so he forms gametes containing either the X chromosome or the Y chromosome in a 1:1 proportion. The individual of the female sex is XX and thus she forms only gametes containing a X chromosome.