The Mysterious Y Chromosome

        One key difference distinguishes men from women: the Y chromosome. This name is a misnomer, since this chromosome resembles a chromosomal fragment rather than the letter Y. Despite the Y chromosome's small size, its biological function is essential to the survival of species. Several genes on this chromosome are important for initiating the development of male sex organs. For example, the SRY (Sex-determining factor Y) gene is responsible for stimulating the formation of testes during embryonic development.

         Questions surrounding the evolution of the Y chromosome have lingered in the minds of scientists since its discovery in 1905. It has been estimated that the Y chromosome lost 97% of its genes during the course of evolution, and researchers believe that there must be a reason why the remaining 3% of genes on the Y chromosome were retained. Until recently, it was unknown whether these genes possessed a selective advantage over the genes that were no longer present. A study in Nature has conducted rigorous genetic analysis of the Y chromosome to gain a better understanding of the genes that have weathered time. David Page's group at the Massachusetts Institute of Technology (MIT) found that the genes that have been shielded from decay are required to maintain proper levels of proteins essential for viability. In other words, loss of these genes on the Y chromosome would result in deficiencies for proteins involved in important biological processes, which can lead to the death of an organism. Thus, this research group concluded that genes found on the Y chromosome play a role in supporting basic cellular processes as well as determining male sex characteristics.

          This finding is intriguing because it sheds light on possible variables that might not be considered in human diseases and disorders. For instance, loss of the Y chromosome can result in developmental disorders such as Turner syndrome, in which an individual has one X chromosome but lacks another functional X or Y chromosome. These individuals appear to be female but often fail to develop mature ovaries, leading to decreased fertility. Turner syndrome also results in other maladies such as hearing loss, scoliosis, and short stature. It is possible that a deficiency in gene dosage due to the lack of an X or Y chromosome is responsible for sex-independent characteristics of this disease. Many of the genes on the Y chromosome are expressed throughout the body, so they will most likely function in capacities that are independent of male sex organs. Furthermore, future studies should investigate the various functions of these genes in male cells and how they contribute to supporting the lives of male organisms.

A human X chromosome (in red) and Y chromosome (in blue).
Courtesy: SPL, http://www.bbc.com/news/health-24991843