How does the protein control sex of a developing embryo?
Sex determination in humans and many other species is primarily controlled by a specific gene called the sex-determining region Y (SRY) gene, which is located on the Y chromosome. The SRY gene encodes a protein known as the sex-determining region Y protein (SRY protein). Here's how the SRY protein controls the sex of a developing embryo:
1. Expression of the SRY gene: The SRY gene is present on the Y chromosome, which is typically found only in males. During early embryonic development, if the embryo carries a Y chromosome, the SRY gene becomes active and starts producing the SRY protein.
2. Initiation of testis development: The SRY protein acts as a transcription factor, which means it can regulate the expression of other genes. One of its primary functions is to trigger the formation of testes, the male sex organs. The SRY protein does this by activating the expression of several genes involved in testis development, such as the SOX9 gene.
3. Formation of the male reproductive system: Under the influence of the SRY protein and other testis-determining factors, the developing embryo forms testes instead of ovaries. The testes then produce hormones such as testosterone, which further drives the development of male reproductive structures, including the penis and scrotum.
4. Differentiation of sex organs: The SRY protein also plays a role in the differentiation of the internal sex organs. It inhibits the development of female reproductive structures, such as the uterus and fallopian tubes, and promotes the formation of male reproductive ducts, such as the epididymis and vas deferens.
5. Secondary sexual characteristics: The SRY protein indirectly influences the development of secondary sexual characteristics associated with males, such as a deeper voice, facial hair growth, and increased muscle mass, by regulating hormone production.
6. Genetic regulation: The SRY protein works in conjunction with other genes and signaling pathways to ensure proper sex determination and differentiation. Its expression is regulated by various genetic factors, including enhancers and silencers, which control the activity of the SRY gene.
In summary, the SRY protein plays a crucial role in sex determination by initiating the development of testes and directing the embryo towards the male developmental pathway. It regulates gene expression and influences the formation of male reproductive organs and secondary sexual characteristics.