Nettie Stevens’ 155th birthday

Nettie Stevens is a American geneticist.

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What are the genetics behind gender?

This simple question drove the work of American geneticist Nettie Stevens. Building on research by Edmund Beecher Wilson and Thomas Hunt Morgan at Bryn Mawr, Stevens discovered the connection between chromosomes and physicality. Her breakthrough evolved into the XY sex-determination system, now taught in classrooms around the world.