Exceptional instances of females possessing the SRY gene have been reported three times in the medical literature, two in 2024 itself.
The SRY gene– Provides instructions for making a protein called the sex-determining region Y protein.
SRY Gene's Role – The SRY gene, located on the Y chromosome, is the primary determinant of maleness.
Its presence typically leads to the development of male characteristics, while its absence leads to female development.
Typical Sex Determination – Eggs carry an X chromosome, while sperm carry either an X or a Y.
XX combinations result in females, and XY combinations result in males.
SRY Translocations – Rarely, the SRY gene can move from the Y chromosome to an X chromosome (a translocation).
Sterile male– If this X chromosome fertilizes an egg, the resulting XX individual usually develops as a sterile male, a man who is unable to reproduce due to a lack of sperm or other reproductive issues.
Exceptional Females with SRY – Cases of fertile females with the SRY gene on an X chromosome are exceptional cases.
Key to Female Development in These Cases – The key difference in these exceptional females lies in a specific deletion on the X chromosome carrying the SRY gene.
This deletion results in the inactivation of the translocated X chromosome during female development.
This "biased" inactivation silences the SRY gene, allowing female development to proceed.
If the other X chromosome were inactivated, the individual wouldn't survive because the deleted genes are essential for life.
Significance – These cases reinforce the SRY gene's importance in male development.
Only when it is silenced (through biased X-inactivation due to the deletion) can female development occur even with the SRY gene present.
Further Research – The article suggests the need for more research to understand the long-term effects of SRY translocations, even when they result in female development.
It also highlights the potential value of screening for such translocations in the future.
