Susumu Ohno

Susumu Ohno was a Japanese-American geneticist and evolutionary biologist whose 1970 book Evolution by Gene Duplication argued that the duplication of genes, and even the duplication of entire genomes, was a major creative force in evolution, providing raw genetic material that could accumulate new mutations and take on new functions without disrupting the original gene existing role; duplicate genes arising from whole genome duplication are now called ohnologs in his honor. Ohno also proposed that the genomes of early vertebrates underwent one or more rounds of complete genome duplication, an idea later known as the two-rounds hypothesis, and he is credited with popularizing the term junk DNA for stretches of the genome with no apparent function. In 1961 he demonstrated that the Barr body, a compact structure long observed in the nuclei of female mammalian cells, was in fact a condensed, inactivated X chromosome, connecting his work directly to the X-inactivation phenomenon described by Mary Lyon. He further showed that the gene content of the mammalian X chromosome has remained remarkably stable across widely different mammalian species, a pattern known as Ohno law. Ohno earned his early degrees in Japan before moving to the United States in 1951 and spending most of his career, from 1952 to 1996, at the City of Hope Medical Center in California.