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Meselson, Matthew (Stanley)

protein helix dna ribosomes

(1930–) US molecular biologist: showed how the DNA double helix replicates.

Born in Colorado, Meselson first studied liberal arts at Chicago and then physical chemistry at Caltech, where he remained to teach physical chemistry. In 1961 he moved to Harvard.

When in 1953 proposed that genes were constructed of a double helix of DNA, they also suggested that, when this duplicated, each new double helix in the daughter cells would contain just one DNA strand from the original helix (‘semiconservative replication’). The alternative would be for one daughter cell to contain both the old strands and the other daughter to receive both new strands (‘conservative replication’). In 1957 Meselson and F W Stahl (1929– ) showed by ingenious experiments using the bacterium Escherichia coli labelled with nitrogen-15 that replication is indeed semiconservative; an important result, verifying Crick and Watson’s ideas and using intact dividing cells without the use of injurious agents.

Meselson also worked on ribosomes, the cell organelles that are the site of protein synthesis. The ribosomes are ‘instructed’ on protein construction by m-RNA and if given abnormal instructions will produce abnormal protein. When a virus invades a bacterial cell, the viral DNA releases its m-RNA, which acts on the bacterial ribosomes, causing them to make viral protein rather than bacterial protein.

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