The Y Chromosome Determines Maleness

There are two sex chromosomes in humans: X and Y.

The Y chromosome determines the male sex and is the smallest chromosome of the human genome.

There are three regions in the Y chromosome: the pseudoautosomal portion, which is further divided into two regions - PAR1 and PAR2, the heterochromatic region, and the euchromatic region.

The S-R-Y gene is located in the euchromatic region of the Y chromosome. It plays a vital role in the development of male fetuses.

When an egg carrying an X chromosome fuses with a sperm carrying a Y chromosome, it forms a zygote.

The zygote then continuously divides to form an embryo. At this stage, male and female embryos are developing along the same pathway and are physiologically identical.

During the early stages of development, the embryo has two precursor organs: the Wolffian duct and the Mullerian duct.

The Wolffian duct can differentiate into male genital structures and the Mullerian duct can differentiate into female genital structures.

In the weeks after fertilization, the S-R-Y gene present on the Y chromosome is transcribed and then translated into the S-R-Y protein. The S-R-Y protein initiates the development of testes in the fetus.

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