Y chromosome

If the test is negative for the Y chromosome - ie it is absent - the athlete is eligible to compete in the female category.

The test for the SRY gene - which is part of the Y chromosome and causes male characteristics to develop - can be conducted via a cheek swab or blood test.

Chromosomes are larger sections of DNA, and male cats like other mammals have an X and a Y chromosome, which carry different amounts of genes.

Genes found on the Y chromosome are only active in cells that have the XY chromosome.

By contrast, there was a lot of diversity in the Y chromosomes, which is passed from father to son, indicating that men from lots of different families married into the community.