The Chain Of Events

1951

MAY Watson attends Maurice Wilkins' lecture on X-ray crystal-lography of DNA

APRIL Linus Pauling deciphers the molecular structure of the protein keratin

OCT. Watson arrives at the Cavendish Laboratory in Cambridge, where he meets Francis Crick

NOV. Watson and Wilkins attend a seminar by Rosalind Franklin. Watson fails to remembers correctly key data about the water content of DNA

NOV. Watson and Crick build a model of DNA as a triple helix. Franklin immediately spots their major blunder

DEC. Watson and Crick are told to back off the DNA project. They send the molds for their models to Wilkins and Franklin in London

1952

MAY The State Department prevents Pauling from leaving the U.S. because of his political views

MAY Franklin takes her famous X-ray image of DNA in its B form

MAY Franklin and Wilkins have a formal falling out. The lab's director assigns Wilkins to work with the B form of DNA and Franklin to concentrate on the A form

1953

JAN. 28 Watson and Crick learn that Pauling has concluded that DNA is a three-stranded molecule

JAN. 30 Watson goes to London to tell Wilkins and Franklin about Pauling's mistake. Wilkins shows Watson Franklin's best image of the B form, which strongly suggests a double helix

FEB. 8 Watson and Crick learn of a report on DNA studies at King's College that convinces them the molecule has two chains

FEB. 19 Watson tinkers with a "pretty" model, unsure of the placement of the backbone or which bases pair with which. That week Watson learns he has been using the wrong chemical form of one of the key bases

FEB. 28 In a eureka moment, Watson realizes the base pairs don't match like with like--A-A or G-G--rather they pair A-T and G-C. Crick concurs, and their model falls into place

APR. 25 Watson and Crick report their discovery in a letter to the journal Nature

1953

George Gamow suggests that DNA holds the code for making proteins

1959

The first human chromosome abnormality, Down syndrome, is identified

1960

Messenger RNA, the link between DNA and the protein-making factories of cells, is discovered

1961

Marshall Nirenberg identifies the first of 64 three-letter genetic codes for proteins

1962

Crick, Watson and Maurice Wilkins win Nobel Prize

1967

Allan Wilson and Vincent Sarich, using the tools of molecular biology, estimate that humans and great apes diverged about 5 million years ago, not 25 million, as many anthropologists believed

1968

Watson's The Double Helix is published and becomes a best seller

1969

A Harvard Medical School team isolates the first gene, a segment of bacterial DNA that plays a role in sugar metabolism

1970

University of Wisconsin researchers synthesize a gene from scratch

Peter Vogt and Peter Duesberg identify the first cancer-causing gene, in a virus

1972

Paul Berg and colleagues cut and splice genes from viruses to create the first molecules of recombinant DNA