Final answer:
The SRY gene on the Y chromosome is crucial for the development of male sexual features by initiating testes formation and promoting male sex differentiation. Absence or mutation of SRY leads to default female development.
Step-by-step explanation:
The SRY gene is responsible for the development of male sexual features. This gene, located on the Y chromosome, initiates a cascade of events that leads to male sex differentiation. In the absence of the SRY gene, the default developmental pathway leads to female sexual features. However, the presence of the SRY gene in males actively recruits other genes that promote testes development while suppressing those involved in female development. This action results in the differentiation of germ cells into spermatogonia for the male reproductive system. Furthermore, the testes secrete hormones such as testosterone, which are essential for the development of other male sex organs.
Without the activity of the SRY gene, an embryo will not exhibit male sexual development, leading to the formation of ovaries and female sexual organs instead. This highlights the critical role of SRY in determining the gender in the context of embryonic development. A mutation or deletion in the SRY gene can result in conditions like Swyer syndrome, where despite having a typically male XY genotype, male sexual characteristics fail to develop.