The SRY gene test for women athletes is misguided — I should know, I discovered the gene in 1990

Sebastian Coe, the president of World Athletics, recently announced a new rule for women athletes that requires them to undergo mandatory genetic tests to verify their biological sex. This test must be done if athletes wish to compete at the World Athletics Championships in Tokyo in September.

World Athletics has said all athletes competing as women must have an SRY gene test to identify whether a male Y chromosome is present. Since the SRY gene is found on the Y chromosome, it is, in effect, a proxy for the Y chromosome.

Any athlete whose test shows the presence of the SRY gene will be banned from competing in the women’s category in elite events. However, if the athlete has a condition called complete androgen insensitivity syndrome, they may be able to qualify for an exemption.

Coe said the decision was made to ensure “the integrity of women’s sport” with World Athletics asserting that the SRY gene is a reliable proxy for determining biological sex.

I argue that the science does not support this overly simplistic assertion. I should know, because I discovered the SRY gene on the human Y chromosome in 1990. I have been researching it and other genes required for testis development for 35 years.

Brief primer on testes and ovary development

If a human embryo has XY chromosomes, then at six weeks of development the SRY gene on the Y chromosome triggers a cascade of events involving about 30 different genes that lead to the formation of testes.

In the simplest terms, the testes then produce hormones including testosterone, leading to male development. However, if an embryo has XX chromosomes, a whole different group of genes come into play, ovaries form and the hormones produced result in a female.

We know that making testes or ovaries requires a complex network of many interacting genes and proteins. Some genes promote testicle development and others promote ovary development.

Other genes either suppress ovary formation or antagonise testicle formation.

Even once ovaries or testes are fully formed, we require other genes to maintain them. These genes don’t always function as expected, affecting the development of these organs.

How does this relate to the sex testing of elite women athletes?

Changes or variants in the many genes that regulate the development of a testicle or an ovary can result in sex reversal or a nonfunctioning testicle or ovary.

What do I mean by this? If there is a change in the SRY gene so that it does not function as usual, then a person can fail to develop testes and be biologically female. Yet they carry XY chromosomes, and under the World Athletics tests they would be excluded from competition. However, athletes can appeal a World Athletics finding if they believe the test result does not reflect their sex.

Other XY individuals may have a functioning SRY gene yet are female, with breasts and female genitalia, for example, but with internal testes.

Importantly, the cells of these people are physically unable to respond to the testosterone produced by these testes. Yet, they would receive positive SRY tests and be excluded from competition.

At the 1996 Olympic Games in Atlanta, eight of 3,387 women athletes had positive test results for a Y chromosome. Of these, seven were resistant to testosterone.

The SRY test isn’t cut and dried

World Athletics asserts that the SRY gene is a reliable proxy for determining biological sex. But biological sex is much more complex, with chromosomal, gonadal (testicle or ovary), hormonal and secondary sex characteristics all playing a role.

Using the SRY gene to establish biological sex is wrong because all it tells you is whether or not the gene is present. It does not tell you how the SRY gene is functioning, whether a testicle has formed, whether testosterone is produced and, if so, whether it can be used by the body.

World Athletics is recommending that all women athletes take a cheek swab or blood sample to test for the presence of the SRY gene. Normally, the sample would be sent to a lab that would extract DNA and look for the presence of the SRY gene.

This may be easy enough in wealthy countries, but what is going to happen in poorer nations without these facilities?

It is worth noting that these tests are sensitive. If a male lab technician conducts the test, he can inadvertently contaminate it with a single skin cell and produce a false positive SRY result.

No guidance is given on how to conduct the test to reduce the risk of false results. Nor does World Athletics recognise the impacts a positive test result would have on a person, which can be more profound than exclusion from sport alone.

There was no mention from World Athletics that appropriate genetic counselling should be provided, which is considered necessary prior to genetic testing and challenging to access in many lower- and middle-income countries.

I, along with many other experts, persuaded the International Olympic Committee to drop the use of SRY for sex testing for the 2000 Sydney Olympics.

It is therefore very surprising that, 25 years later, there is a misguided effort to bring this test back.

Given all the problems outlined above, the SRY gene should not be used to exclude women athletes from competition. DM

First published by The Conversation.

Editor’s note: this article has been amended to clarify what the SRY test reveals and to add details of potential exemptions under the World Athletics proposals.

Andrew Sinclair is deputy director of the Murdoch Children’s Research Institute in Melbourne, Australia.

This story first appeared in our weekly Daily Maverick 168 newspaper, which is available countrywide for R35.