Susumo Ohno's long and productive scientific career, influential in many areas of biology and genetics, was begun because of his love of horses. Ohno received his DVM from the Veterinary College of the Tokyo University of Agriculture and Technology in 1949. He also earned a PhD. in pathology and a DSc. in cytogenetics from Hokkaido University in Japan.

In 1952, Ohno took a research position at the City of Hope National Medical Center in Duarte, California, and there he stayed for almost half a century. One of his earliest contributions was the demonstration that the Barr body was actually the inactive X chromosome in females. This observation paved the way for the Lyon hypothesis.

His studies of the X chromosome also led him to formulate Ohno's Law. Although genes are known to be juggled between different autosomes in the course of evolution, Ohno theorized that genes on the X chromosome...