What makes the Y chromosome so special (despite having far fewer genes than its X counterpart) is that it contains the SRY gene, which is responsible for kick-starting male development in the embryo.

World Athletics president Sebastian Coe announced the genetic test after proposals to tighten eligibility rules in women's events were discussed.

Officials said in February that the test is looking for the SRY gene, according to Sky News. The specific gene "provides instructions for making a protein called the sex-determining region Y protein.

These tests will screen athletes’ genetic samples to determine whether they contain the SRY gene, or “a genetic surrogate for a Y chromosome,” according to the organization. The decision ...