8 JUNE 1916 * 28 JULY 2004
FRANCIS CRICK, on whose behalf it would not be unreasonable to claim that he was the greatest and most influential theoretician of biology since Charles Darwin, died of colon cancer in La Jolla, California, on 28 July 2004, at the age of eighty-eight. My declaring that Crick was a "theoretician of biology" is not meant to imply that his main scientific interest concerned the working out of the quantitative relations that govern the behavior of complex biological systems. Rather, by calling him a "theoretician" I want to indicate that, like Darwin's main scientific interests, Crick's also lay in developing novel qualitative concepts that can account for previously unfathomed aspects of life.
Crick was born in Northampton, England, on 8 June 1916. On completing his secondary education at Northampton Grammar School he went to University College, London, where he received a B.Sc. in 1937. He stayed on to do graduate work for a Ph.D. in physics. However, in 1939 his studies at University College were interrupted by the outbreak of war. During the war, Crick worked at the British Admiralty in London, devising detonators for magnetic and acoustic mines. Very likely, all that time a hapless German Anti-Crick sat at the Kriegsmarineamt in Wilhelmshaven, locked in a battle of wits with the future greatest theoretician of biology since Darwin in the design of ever more sophisticated mines able to discriminate between the approach of real enemy ships and dummy decoys.
THE DNA DOUBLE HELIX
Crick left London and the Admiralty in 1947 and went up to Cambridge for graduate studies in biology at the Strangeways Laboratory. He was not thrilled, however, by the research project assigned to him there-a study of the viscosity of the cytoplasm. So he moved to the Cavendish Laboratory, the renowned Cambridge center for the determination of molecular structures by X-ray crystallography. At the Cavendish, Crick joined the research group headed by Max Perutz and John Kendrew and began an X-ray crystallographic study of protein structure for his Ph.D. thesis.
A crucial event in Crick's career occurred in 1951, when James Watson, a young American postdoctoral student trained in the formal genetics of viruses and bacteria but hitherto a stranger to X-ray crystallography, turned up at the Cavendish. Watson was bent on determining the structure of the DNA molecule, in which the genetic information carried in the chromosomes of living creatures had recently been found to be encoded. Chemical analysis of DNA had shown it to consist of long chains of nucleotides, each nucleotide consisting of the five-carbon sugar deoxyribose, to which one of two kinds of purine bases-adenine and guanine-or one of two kinds of pyrimidine bases-thymine and cytosine-is attached. The nucleotides are linked via phosphate diester bonds, which join many consecutive deoxyribose moieties, thus forming a polynucleotide chain.
Watson and Crick undertook a collaborative X-ray crystallographic study of DNA at the Cavendish, which, by the spring of 1953, had culminated in their discovery that the DNA molecule is a double helix, composed of two intertwined polynucleotide chains, held together by hydrogen bonds formed between an adenine and a thymine, or between a guanine and a cytosine, on opposite sides of the double helix.
THE CENTRAL DOGMA
At first sight, Watson and Crick's discovery of the double helical structure of the DNA molecule resembled Linus Pauling's-by then two-year-old-discovery of the helical structure of protein molecules, in that the formation of intramolecular hydrogen bonds also has an important role in shaping Pauling's protein helix. At second sight, however, the discovery of the DNA double helix emerged as an event with much greater heuristic consequences. It opened up enormous vistas for the imagination and led Watson and Crick to their formulation of what came to be known as the "central dogma of molecular biology. …