The Role of the SRY Gene in Determining Sex

The Role of the SRY Gene in Determining Sex

Sub: Sci

Sec: Health

Why in News

• Recent studies from the Renato Dulbecco University Hospital in Italy and the Cincinnati Children’s Hospital Medical Center, USA, have reported exceptional cases of females possessing the SRY gene. These findings, published in Genes and Molecular Genetics and Genomic Medicine, respectively, provide new insights into the gene’s role in sex determination.

About SRY Gene:

• Sex-determining Region Y (SRY) gene is found on the Y chromosome.
• Ait acts as a transcription factor, initiating male sex determination by promoting the development of testes.
• Role in Sex Determination: The SRY protein binds to DNA, causing it to bend and alter its structure. This binding regulates the expression of other genes crucial for testis formation, such as SOX9.
• In typical male development, the presence of the SRY gene leads to the differentiation of the bipotential gonads into testes.
• The testes then produce male hormones, including testosterone, which guide the development of male secondary sexual characteristics.
• 46,XX Testicular Disorder of Sex Development:  Occurs when the SRY gene is translocated to an X chromosome.
  • Individuals have two X chromosomes but develop male characteristics due to the presence of the SRY gene.
  • Such individuals are typically sterile due to the absence of other Y chromosome genes necessary for spermatogenesis.
• Swyer Syndrome (46,XY Gonadal Dysgenesis): Results from mutations or deletions in the SRY gene.
  • Individuals have an XY karyotype but develop female characteristics because the defective SRY gene fails to initiate testis development.
  • They possess undeveloped gonads and do not undergo puberty without hormone replacement therapy.
• Ongoing studies aim to understand the regulatory networks involving the SRY gene and its interactions with other factors like SF1, WT1, and DAX1.
• Y Chromosome Degeneration: Research indicates that the Y chromosome, which houses the SRY gene, is degenerating and may disappear in a few million years.

Exceptional Cases of SRY Gene in Females:

• In rare cases, the SRY gene can be transferred from the Y chromosome to the X chromosome due to a mutation known as a translocation.
• When a sperm carrying an X chromosome with an SRY translocation fertilizes an egg, an XX individual with the SRY gene is born.
• In most cases, XX individuals with the SRY gene develop testes and become biological males.
• However, these individuals remain sterile, as they lack other Y chromosome genes required for sperm production.

Chromosomal Basis of Sex Determination:

• Human reproductive cells (eggs and sperm) contain 23 chromosomes, including one pair of sex chromosomes (XX for females, XY for males).
• Egg cells always carry an X chromosome, while sperm may carry either an X or a Y chromosome.
• The combination at fertilization determines the baby’s sex: XX results in a female, while XY results in a male.