Clement Lawrence Markert (April 11, 1917 – October 1, 1999) was an American biologist credited with the discovery of isozymes (different forms of enzymes that catalyze the same reaction). He was a member of the National Academy of Science and American Academy of Arts and Sciences, and served as president of several biology societies.
Markert was born in Las Animas, Colorado and raised in Pueblo, Colorado. He attended the University of Colorado, and in 1937, left college to fight in the Spanish Civil War—stowing away aboard a freighter to circumvent government travel restrictions. After returning to college, Markert completed his bachelor's degree in 1940; upon graduation, he married Margaret Rempfer, and they moved to UCLA for graduate work. He enrolled in the United States Merchant Marine to take part in World War II; by 1954 they would have three children. After the war, he finished a master's degree at UCLA followed by a Ph.D. from Johns Hopkins University in 1948.
Markert's Ph.D. research, and subsequent postdoctoral work at Caltech, focused on the sexuality and other physiological and genetic aspects of Glomerella, a genus of pathogenic plant fungi. At Caltech, he also worked with George Beadle on corn and Neurospora genetics.
In 1950 he began teaching at the University of Michigan, part of the new wave of what would become molecular biology. In 1954, Markert became a victim of McCarthyism; he was suspended from teaching because he refused to testify before the House Un-American Activities Committee. He was later reinstated, and continued at the University of Michigan until moving to Johns Hopkins in 1957, followed by Yale University—as head of the Department of Biology. In 1966, he served as president of the American Institute of Biological Sciences. He remained at Yale until retiring in 1986 to North Carolina State University, where he continued researching until 1993.
Early in his career, Markert developed the concept of isozymes based on electrophoresis and histochemical staining of enzymes. He found that often what had been assumed to be a single enzyme catalyzing a specific reaction was in fact multiple enzymes, with different proteins present in different tissues. In biochemistry, this forced a re-evaluation of some basic assumptions of enzyme kinetics; in genetics, it contributed to the shift from the "one gene-one enzyme hypothesis" to the "one gene-one polypeptide" concept. Markert's early work with isozymes, many of which are formed by gene duplication, was a precursor to the concept of gene families. Markert's later career focused on developmental biology, particularly developmental genetics in experiments with mosaic animals.
In 1990, the University of Michigan created the annual "Davis, Markert, Nickerson Lecture on Academic and Intellectual Freedom" series, in honor of Markert and two other Michigan faculty suspended for refusing to testify in 1954.
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