The First Sex-Determining Genes

In a recent study, scientists at the Swiss Institute of Bioinformatics examined when X and Y chromosomes began to differentiate. These “sex genes”, the Y chromosome in particular, are ultimately responsible for all the morphological and physiological differences between males and females. The team examined male tissues from the testicles from different species of the three major mammalian lineages. They looked at humans, apes, rodents and elephants, which made up the placental lineage, opossums and kangaroos which are from the marsupial lineage, and egg-laying mammals known as the monotreme lineage. Rather than sequencing all of the Y chromosomes, the research team decided to compare the genetic sequences from male and female tissues and eliminated all common sequences between both sexes in order to keep only the sequences that corresponded to the Y chromosome. By taking this route the team created the largest gene atlas of the Y chromosome to date. The study established that the first “sex genes” appeared together in mammals around 180 million years ago. The sex-determining gene named SRY in placentals and marsupials had formed in the common ancestor also around 180 million years ago. The AMHY gene, accountable for the emergence of Y chromosomes in monotremes, appeared some 175 million years ago. Both of these genes emerged at nearly the same time but totally independent of one another. Although they found when these genes emerged it is still unclear what the nature of the sex-determination system in the common ancestors of all mammals was.

This study can stand as a basis for further research on what determines the development of the Y chromosome. It can fuel future research on what influences contributed to why an individual is born male or female. It can help reveal if these factors were even related to the sex chromosome or if they were environmental such as temperature. By laying the ground work and putting in over 29,500 computing hours and creating the largest gene atlas of the Y chromosome, this research may help answer these questions and many others relating to the sex genes.

Article Link: http://www.sciencedaily.com/releases/2014/04/140423151035.htm

Related Link: http://www.biology-online.org/2/6_sex_chromosomes.htm