Cavendish Semiquincentennial: Nettie Stephens PHD

Nettie Stevens was born in Cavendish in 1861. The child of working-class parents, Stevens was raised during a time when women's educational opportunities were limited. In spite of this, Stevens ultimately received a PH.D. from Byrn Mawr and was given an assistantship by the Carnegie Institute. In 1905, her work on sex determination was published. Investigating mealworms, she found female cells contained 20 chromosomes, but male cells contained 19 large chromosomes and one very small one. She showed that the X body paired with a 20th, much smaller chromosome in meiosis. She proposed that these two chromosomes be called X and Y, and explained that females contained two X chromosomes. Some believe her position in the field of genetics has largely been ignored because the credit for the discovery of X and Y chromosomes and their role in determining gender is instead generally given Edmund B. Wilson, who had read Stephens’ manuscript on chromosomal patterns before publishing his own theory, and T. H. Morgan, the biologist with whom Wilson shared the Nobel Prize for the discovery. Stevens died in 1912. Women in Technology News, Fall, 1994, Vol. 11, No. 1