Lee Hartwell

Leland Harrison (Lee) Hartwell (born October 30, 1939, in Los Angeles, California) is former president and director of the Fred Hutchinson Cancer Research Center in Seattle, Washington. He shared the 2001 Nobel Prize in Physiology or Medicine with Paul Nurse and Tim Hunt, for their discoveries of protein molecules that control cell division.
When cells divide, they divide in phases called G1 (growth), S (synthesis), G2 (growth), and M (mitosis). Nurse, Hartwell and Hunt together discovered two proteins, cyclin and CDK (cyclin dependent kinase), which control the change from one stage to another. These proteins are called "checkpoints", because they check whether the cell has divided properly. If the cell does not divide correctly, other proteins will try to repair it. If that does not work, they will destroy the cell. If a cell divides incorrectly and survives, it may cause cancer and other serious diseases.
Working in baker's yeast ("Saccharomyces cerevisiae"), Hartwell identified the fundamental role of checkpoints in cell cycle control, and CDC genes such as CDC28, which controls the start of the cycle – the progression through G1.