New Genetic Discovery Determines Baby’s Sex

A new study using a genetic regulator can determine a baby’s sex. It can also dictate whether the reproductive system may develop differently after birth.

Researchers at the Murdoch Children’s Research Institute in Melbourne, Australia have recently made this discovery, which adds insight into how the sex of a baby is determined. The scientists learned that it doesn’t simply involve the XY and XX chromosomes, but a regulator that can raise or lower the activity of the unborn baby’s genes. This genetic regulator can determine whether a child ultimately becomes male or female.

Genetic Makeup Can Determine Sex or a Sex Disorder

Brittany Croft, MCRI researcher and Ph.D. student of Hudson Institute, stated that a baby’s chromosome makeup determines its sex at conception. She added that the Y chromosome includes a gene called SRY that can work with another gene, SOX9, which begins the development of testes, and that high levels of it are required for the testes to develop normally. She stressed that a disruption in the activity to the SOX9 gene can result in a baby’s having disorders in its sex development.

Intersex Development

A disorder of sex development, also simply known as “intersex,” is a condition that results in a combination of both male and female characteristics in a baby.

Unfortunately, there is little understanding of the condition, which affects around one out of every 4,500 to 5,500 people. The researchers studied 44 people with these characteristics and determined three enhancers they identified in noncoding DNA that controlled the levels of the SOX9 gene. While looking at samples, the scientists noted that two individuals with XX chromosomes and high levels of SOX9 developed testes instead of ovaries. Likewise, it was discovered that two people with XY chromosomes who had low levels of the SOX9 gene developed ovaries instead of testes.

Professor Andrew Sinclair, the lead author of the study, said that the enhancers are located within the DNA, outside of the genes. He referred to them as “junk DNA” or “dark matter” and explained that around 90 percent of DNA comprises these parts and that learning more about these enhancers can potentially make for a better understanding of DNA in general.

Professor Sinclair further stated that around one million enhancers control around 22,000 genes. He elaborated that the goal of the study was to gain a better understanding of the way in which the SOX9 gene is regulated by those enhancers and whether it was possible to disrupt the enhancers and see if this would result in sex-development disorders.

The Future of Intersex Research

Currently, when researchers check for the causes of intersex characteristics, noncoding DNA areas are not included. However, after the findings, this could possibly change.

Croft stated that the findings are significant and that the gain or loss of the enhancers is required for normal sex development. She stressed the need to look outside the genes and at the enhancers, to which Sinclair agreed and said the dark matter of DNA is the key to better diagnosing sex-development disorders.