The SRY gene (Sex-determining Region Y) is a gene located on the Y chromosome in humans and many other mammals. It plays a crucial role in male sex determination by triggering the development of testes, which produce male hormones. This process leads to the formation of male physical characteristics. When the SRY gene is active, it initiates a cascade of genetic events that promote male development. In the absence of the SRY gene, the default pathway leads to female development. Thus, the presence or absence of this gene is fundamental in determining an individual's sex.