The Chain Of Events

By Sora Song and Andrea Dorfman

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

Bruce Ames discovers that cancer-causing chemicals also cause mutations in DNA, the basis of the Ames test for carcinogens

1973

In the first successful genetic-engineering experiment, Stanley Cohen and Herbert Boyer insert a gene from an African clawed toad into bacterial DNA

1975

Scientists meet at the Asilomar conference center in California and call for guidelines regulating recombinant-DNA research

1976

Boyer and Robert Swanson found Genentech, the world's first genetic-engineering company

1977

Walter Gilbert and Frederick Sanger separately develop methods for sequencing DNA

1978

Genentech scientists help clone the gene for human insulin

1980

Martin Cline and co-workers create a transgenic mouse by transferring functional genes from one animal into another

1982

The U.S. Food and Drug Administration approves the first genetically engineered drug, a form of insulin produced by bacteria

Stanley Prusiner discovers prions, the infectious proteins responsible for scrapie and mad-cow disease

Thomas Cech, and later Sidney Altman, show that RNA can act as an enzyme

1983

Kary Mullis devises the polymerase chain reaction (PCR), enabling scientists to multiply rapidly snippets of DNA 1984

Alec Jeffreys and colleagues develop genetic fingerprinting--using DNA to positively identify individuals

Elizabeth Blackburn and Carol Greider discover telomerase, an enzyme that extends the life of cells

1985

Robert Gallo and Luc Montagnier each publish the genetic sequence of HIV, the virus that causes AIDS

1986

Leroy Hood invents the first automatic DNA sequencer

The FDA approves the first genetically engineered vaccine for humans for hepatitis B

1987

Allan Wilson, Rebecca Cann and Mark Stoneking determine that all living humans share a common ancestor: "mitochondrial Eve"

1988

Harvard University acquires the first patent for a genetically altered animal: a mouse that is highly susceptible to breast cancer

1989

The first genetic screening test (to determine sex) is performed on embryos before they are implanted in the uterus

1990

The Human Genome Project, an international effort to map and sequence human DNA, is officially launched

1993

Researchers at George Washington University clone the first human embryos, and nuture them in vitro for several days

1994

The FDA allows the first genetically modified food product to market, the Flavr Savr tomato. A bland taste and high price make it a commercial dud

1995

PCR and DNA fingerprinting play a starring role in the O.J. Simpson murder trial

Craig Venter and colleagues are first to decode the genome of a free-living organism, the bacterium Haemophilus influenzae

DNA microarrays are invented, permitting rapid analysis of large quantities of DNA

Mutations in the BRCA1 and BRCA2 genes are linked to hereditary breast, ovarian and prostate cancers

1997

Ian Wilmut and others report they have cloned a sheep, Dolly

1998

Two teams grow embryonic stem cells in a Petri dish

1999

First known American death caused by gene therapy: Jesse Gelsinger, 18, dies of multiple-organ failure after receiving an experimental treatment

Ingo Potrykus and Peter Beyer create golden rice, a bioengineered strain enriched with beta-carotene

2000

Venter and Francis Collins announce together that they have sequenced the human genome

2002

Scientists at Texas A&M University clone a house cat, which they name cc

Gene-therapy trials in France and the U.S. for the bubble-boy disease are halted after a child undergoing treat-ment develops a leukemia-like disease

Raelian sect claims the birth of the first cloned human baby, named Eve, but offers no proof

2003

50th anniversary of Watson and Crick's discovery of the double helix

Britain's Royal Mint is scheduled to issue a -L-2 coin commemorating the event --By Sora Song and Andrea Dorfman