The genome of human beings is organized into twenty-three chromosome pairs, of which only one pair is responsible for sex determination, with each parent contributing to one chromosome out of the two. The X and Y are the two sex chromosomes that will determine the sex of an embryo (Szalay, 2017). It is notable that mothers only pass on X chromosomes to their children. In terms of fathers, females inherit the X chromosome for the XX genotype from them, and males will inherit a Y chromosome from the father to form the XY genotype. Therefore, the Y chromosome is essential in terms of its presence or absence because it has the genes that will prevent the default biological development and cause the formation of the male reproductive system. This means that the biological default entails the development of the female reproductive system.
In genealogy, the lineage of males within a family is traced through the Y chromosome because it can only be passed down by the father. The Y chromosome is the defining one in determining the male sex and is one-third the size of the X chromosome. It contains fifty-five genes, while the X chromosome contains around nine hundred. The Y chromosome contains the SRY gene that causes the emergence of testes to form an embryo, later resulting in the development of external and internal male genitalia. If a mutation has occurred in the SRY gene, it is possible that the embryo will have female genitalia formed regardless of the XY chromosome pair.
It is also notable that a variation in the number of sex chromosomes in a cell is a common occurrence. For example, some men may have more than two chromosomes in all of their cells, which is referred to as the Klinefelter syndrome, characterized by the XXY variation (“Klinefelter syndrome,” 2020). Besides, it is possible for men to lose the Y chromosome with age, while smoking can also increase the rate of the loss. Some genes that were considered to be lost from the Y chromosome can actually relocate to other chromosomes. Most of the Y chromosome is made up of repeating DNA segments, which means that specialized technology is needed to determine the arrangement of the highly similar segments. Moreover, it is notable that many health conditions are considered to be associated with changes in genes that are expressed on the Y chromosome, and more research is currently being done in this area.
The X chromosome is much larger in size than the Y counterpart. It is carried by the egg, which means that females, who have eggs, can only pass on the X chromosome to their offspring. It is also notable that there is quite a large number of genes to be found in the X chromosome. It has been estimated that there are around 155 million base pairs, which can translate to between 900 to 1,4000 genes embedded into the X chromosome. This means that the chromosome is responsible for carrying around 5% of a human’s total DNA in the entire cell (National Human Genome Research Institute, 2021). Considering the genes that the X chromosome carries, it is more often than sex-related disorders will be included in the X chromosome. Since there is no protective mechanism that safeguards against the mutations, they are more predominant in males than females.
References
Klinefelter syndrome. (2020). Web.
National Human Genome Research Institute. (2021). X chromosome. Web.
Szalay, J. (2017). Chromosomes: Definition & structure. Web.