Final answer:
The SRY gene on the Y chromosome produces a transcription factor critical for male sexual development, prompting the differentiation of bipotential gonadal tissue into testes and repressing female genitalia development. Mutations in the SRY gene can lead to conditions like Swyer syndrome, where an XY embryo does not develop male characteristics. Testosterone further influences this developmental process.
Step-by-step explanation:
Role of the SRY Gene in Male Sexual Development
The SRY gene, located on the Y chromosome, is essential in determining male sexual development. It encodes a transcription factor that interacts with another protein known as SF1. Together, these proteins initiate the expression of certain genes that are crucial for the development of testes from undifferentiated gonadal tissue. Changes or mutations in the SRY protein or SF1 could significantly affect this process.
In the human embryonic stage, both male and female embryos possess bipotential gonadal tissue that can develop into either testes or ovaries. The presence of the SRY gene stimulates a cascade of events that lead to the differentiation of this tissue into testes and the suppression of female gonadal development. Specifically, primary sexual characteristics in males are induced as germ cells in the bipotential gonads differentiate into spermatogonia, which is the first stage in sperm development.
If the SRY gene is deleted or mutated, such as in Swyer syndrome, the embryo with an XY genotype may not develop typically male sex characteristics. Conversely, without the SRY gene expression, as in typical XX genotype embryos, oogonia and primordial follicles would form, leading to female sexual characteristics. Thus, the SRY gene acts as a master regulator in the genetic mechanism underlying sex differentiation.
It is important to note that testosterone production by Leydig cells in the embryonic testes further stimulates the development of male sexual organs. In the absence of such testosterone or the SRY gene, an embryo will tend to develop female sexual organs and structures.