Matthew Meselson

Dr. Matthew Stanley Meselson (born 1930) is an American geneticist and molecular biologist whose research was importatant in showing how DNA replicates, recombines and is repaired in cells.

He began studying chemistry and graduated from the University of Chicago in 1951. He went on to study under Linus Pauling who assigned him work on x-ray crystallography which he later wrote a thesis on in 1958. He started in Harvard in 1961 as associate professor and taught undergraduate genetics for many years.

In 1957 with Frank Stahl he showed that DNA replicates semi-conservatively. The Meselson-Stahl experiment used the Escherichia coli grown in the presence of the nitrogen isotope nitrogen-15, which was then switched to be grown with normal nitorgen, nitrogen-14. When they extracted the DNA using density centrifugation they found three types of DNA, one containg nitrogen-15, one containg nitrogen-14, and a hybrid containing both isotopes. When the hybrid DNA was made single stranded by heating, they could show one parental strand and one that had been newly synthesised, so when DNA is synthesised the DNA double helix splits into two, each of the single strands acting as a template for the synthesis of a complementary strand. This phenomenon is called semi-conservative DNA replication.

He showed in the years that followed many more theories in relation to this with the help of Jean Weigle . in 1961 with Frank Stahl, Sidney Brenner and François Jacob he later demonstrated that ribosomal RNA molecules are stable, which later proved the existance of mRNA - a problem scientists had struggled with previously. He later showed with Charles Radding that genetic recombination results from the splicing of DNA molecules. He also demonstrated the enzymatic basis of a process by which cells recognize and destroy foreign DNA, and discovered methyl-directed mismatch repair, which enables cells to repair mistakes in DNA.

In 1963 Meselson served as a resident consultant in the US Arms Control and Disarmament Agency, since then he has been involved in chemical and biological weapons disarmament policy formation as a consultant and through the Harvard Sussex Program, a disarmament think-tank.

Reference

• Matthew Meselson
• The Meselson - Stahl Experiment