Which geneticist showed in 1905 that chromosomes determine sex in mealworms?
Answer
Nettie Stevens
Nettie Stevens showed in 1905 that chromosomes determine sex in mealworms.
Studying beetles of the genus Tenebrio, Stevens observed that females produced eggs with an X chromosome, while males produced sperm carrying either an X or a much smaller Y chromosome. The combination formed at fertilization determined whether the offspring developed as female or male.
Her findings provided strong cytological evidence for the chromosome theory of sex determination. Edmund Beecher Wilson published related observations independently around the same time, so historical accounts often discuss their work together.
Stevens’s discovery is sometimes simplified as the discovery of “the sex chromosome,” but the important result was more specific: the differing X and Y chromosome complements explained the observed sex ratio and inheritance pattern in the organism she studied.