Clues to DNA

Cavendish laboratoryThe DNA molecule became the focus of growing investigation in the late 1930s and 1940s.

William Astbury carried out perhaps the most important foundation work at Leeds University. Astbury interrogated proteins and nucleic acids with x-rays, obtaining the first diffraction photographs of calf thymus DNA in 1938. Though his data were rudimentary, his findings proved highly influential.

The same year, A Signer, T Capersson and E Hammerstein showed that the bases in DNA lay with their planes roughly perpendicular to the length of the thread-like molecule.

Crucially, in 1944, Oswald Avery, a bacteriologist and research physician in New York, and colleagues Colin Macleod and Maclyn McCarty, demonstrated that DNA carries the genetic code in bacteria, following up little known but crucial work on genetic transformation carried out by Frederick Griffith in London in 1928.

Max PerutzThe realisation that DNA played a key role in heredity, now led to numerous experiments aimed at deducing its structure.

Max Delbruck and Salvador Luria also carried out important studies in the early 1940s at Cold Spring Harbor and elsewhere that suggested an important role for the molecule in chromosomal activity and bacterial transformation and which pointed to the implication of DNA and not protein in genetic processes.

Together with Alfred Hershey, they were awarded the Nobel Prize for Physiology or Medicine in 1969 for this work on genetic replication.

Luria’s experiments in particular influenced the younger generation of researchers, and in 1948, James Watson joined his laboratory at Indiana University as a graduate student.

Attention shifted to the University of Cambridge when, in 1948, the chemist Max Perutz established a protein x-ray laboratory within the Cavendish Laboratory, and which was funded by the Medical Research Council.

Meanwhile, in 1950 Erwin Chargaff, a chemist in New York, found a pattern in DNA’s chemical letters — guanine, cytosine, adenine and thymine — that provided a valuable hint to its structure.

Scientists were closing in on the secret of life.

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