The XY sex-determination system is a sex-determination system used to classify many mammals, including humans, some insects (Drosophila), some snakes, some fish (guppies), and some plants (Ginkgo tree). In this system, the sex of an individual is determined by a pair of sex chromosomes. Females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males have two different kinds of sex chromosomes (XY), and are called the heterogametic sex.[1] So a 'female' boxers tests positive for XY chromosomes and is not disqualified, but in 2020 a female runner test positive for THC and is disqualified. Makes sense. Sha’Carri Richardson, a Track Sensation, Tests Positive for Marijuana