Nettie Stevens

American geneticist (1861–1912)

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Born: Nettie Maria Stevens , ( 1861-07-07 ) July 7, 1861, Cavendish, Vermont , United States
Died: May 4, 1912 (1912-05-04) (aged 50), Baltimore, Maryland , United States
Education: Westford Academy , Westfield Normal School , Stanford University (BA , MA) , Bryn Mawr College ( PhD )
Known for: XY sex-determination system
Fields: Genetics
Institutions: Bryn Mawr College , Carnegie Institution of Washington
Thesis: Further studies on the ciliate Infusoria, Licnophora and Boveria (1903)
Doctoral advisor: Thomas Hunt Morgan
Doctoral students

Article

Nettie Maria Stevens (July 7, 1861 – May 4, 1912) was an American geneticist who discovered sex chromosomes. In 1905, soon after the rediscovery of Mendel's paper on genetics in 1900, she observed that male mealworms produced two kinds of sperm, one with a large chromosome and one with a small chromosome. When the sperm with the large chromosome fertilized eggs, they produced female offspring, and when the sperm with the small chromosome fertilized eggs, they produced male offspring. The pair of sex chromosomes that she studied later became known as the X and Y chromosomes.

Early life