Matthew Meselson. Portrait of Matthew Stanley Meselson (born 1930), American molecular biologist. In 1957 Meselson and Franklin Stahl showed that when the double helix of deoxyribo- nucleic acid (DNA) duplicates during cell division, the two daughter cells each receive one old strand and one new strand. This 'semiconserv- ative' replication was proved using DNA which had been labelled with radioactive nitrogen. Meselson also studied viral infection with Brenner and Jacob, proving that when a virus invades its host, it uses ribonucleic acid (RNA) to instruct its host's ribosomes to begin making viral protein. Photograph taken in 1964.