Matthew Meselson, in collaboration with biologist Franklin W. Stahl, showed experimentally that the replication of deoxyribonucleic acid (DNA) in bacteria is semiconservative. Semiconservative replication occurs in a double stranded DNA molecule when the two strands are separated and a new strand is copied from the parental strand to produce two new double stranded DNA molecules. The new double stranded DNA molecule is semiconservative because only one strand is conserved from the parent; the other strand is a new copy. (Conservative replication occurs when one offspring of a molecule contains both parent strands and the other molecule offspring contains newly replicated strands) The classical experiment revealing semiconservative replication in bacteria was central to the understanding of the living cell and to modern molecular biology.

Matthew Stanley Meselson was born May 24, 1930, in Denver, Colorado. After graduating in 1951 with a Ph.D. in liberal arts from the University of Chicago, he...