What decides whether a baby reptile is a boy or a girl? For people, the answer is chromosomes, the packages of DNA we get from our parents. For many reptiles, the answer is the temperature of the nest. And for some, it is both. In genotypic sex determination (GSD), sex is set the moment the egg is fertilized, by the sex chromosomes the parents contribute. Humans work this way: a mother gives an X, a father gives an X or a Y, and XX makes a girl while XY makes a boy. Many reptiles use a system like ours. Others flip it: in some lizards and snakes, males have matching chromosomes (called ZZ) and females have the mismatched pair (ZW).
This lesson is part of Certified Junior Herpetologist. Enrollment is self-paced, with no deadline to finish (about 30 hours).
