Stevens Nettie Marie


(stē′vənz), Nettie Marie 1861-1912.
American biologist who identified the role of X and Y chromosomes in determining the sex of an organism. Stevens studied the chromosomes of mealworm beetles, first establishing that chromosomes are inherited in pairs. She later showed that eggs fertilized by X-carrying sperm produced female offspring, while Y-carrying sperm produced a male. She extended this work to studies of sex determination in various plants and insects.