Francis Crick

Francis Harry Compton Crick was born on 8 June 1916 in Weston Favell, then a small village near Northampton, England, where his father and uncle ran a boot and shoe factory. As a child he was drawn to science and books, and by the age of twelve had decided he preferred scientific explanations over religious ones. He studied mathematics, physics, and chemistry at Mill Hill School in London on a scholarship, and went on to earn a Bachelor of Science degree from University College London in 1937.

Crick began a PhD at University College London measuring the viscosity of water at high temperatures — work he later described as the dullest problem imaginable. World War II interrupted his studies, and he spent the war years working for the Admiralty Research Laboratory on the design of magnetic and acoustic mines. When peace came, he made a deliberate and difficult shift away from physics toward biology, later describing the transition as almost like being born again. By 1949 he had joined Max Perutz and John Kendrew at the Cavendish Laboratory in Cambridge, where he taught himself the mathematical theory of X-ray crystallography and began work that would define his career.

Late in 1951, Crick began working with the young American biologist James Watson at the Cavendish Laboratory. Watson was only 23 but already held a PhD; Crick was 35 and still a graduate student because of his wartime interruption. The two shared a conviction that the structure of DNA could be worked out through a combination of theoretical reasoning, model building, and existing experimental data. Their chief competition was the eminent chemist Linus Pauling, who had recently identified the alpha helix structure of proteins.

Critical to their success was X-ray diffraction data gathered at King's College London by Rosalind Franklin and her student Raymond Gosling. Watson attended a talk by Franklin in late 1951 and was shown an X-ray photograph of DNA by Maurice Wilkins in January 1953. Crick received a Medical Research Council progress report containing some of Franklin's crystallographic calculations in February 1953. Franklin was unaware that her data had been shared in this way. Her work established that the phosphate backbones of DNA face outward toward water and helped confirm the antiparallel orientation of the two strands — both features that appear in the final model.

The discovery was made on 28 February 1953, and the Watson and Crick paper appeared in Nature on 25 April 1953. A key insight that completed the model came from Watson's work with cardboard cut-out models of the nucleotide bases, through which he recognised that an adenine-thymine pair and a guanine-cytosine pair are structurally similar in length — consistent with the experimentally determined ratios of bases that Erwin Chargaff had established. This base-pairing rule explained how the two strands could serve as complementary templates for copying genetic information. Crick completed his PhD in 1954, with a thesis on X-ray diffraction of polypeptides and proteins.

After the double helix model was published, Crick turned his attention to the biological question of how the sequence of bases in DNA specifies the sequence of amino acids in proteins. He introduced the term 'central dogma' to capture the idea that genetic information flows from DNA to RNA to protein, and that this final step is irreversible — information does not flow back from proteins to nucleic acids. He was careful to note that he used the word 'dogma' not to imply an unquestionable rule but to describe a compelling idea that still lacked solid experimental proof.

In 1956, Crick proposed the existence of small adaptor molecules that would match short sequences of nucleotide to specific amino acids — molecules later identified as transfer RNAs. He laid out, in a 1958 paper, what became the conceptual framework of molecular biology: genetic information stored in DNA, carried to the cytoplasm by a messenger RNA, and translated into protein by ribonucleic-protein complexes now known as ribosomes. An important step came on 15 April 1960, when Crick and Sydney Brenner realised in conversation with François Jacob that messenger RNA and ribosomal RNA are distinct molecules. Later that same summer, Brenner, Jacob, and Matthew Meselson conducted an experiment that provided the first proof of messenger RNA's existence.

The genetic code was eventually shown to be a degenerate triplet code, meaning that most of the 64 possible three-nucleotide sequences code for one of just 20 amino acids. Proof came partly from genetics experiments in which Crick participated, and partly from biochemical work by Marshall Nirenberg and others who used synthetic RNA molecules to drive protein synthesis in the laboratory. When Nirenberg first announced his results at a 1961 conference in Moscow, Crick was so impressed that he immediately invited Nirenberg to repeat the talk for a larger audience. In 1962, Crick, Watson, and Wilkins were jointly awarded the Nobel Prize in Physiology or Medicine for their work on the molecular structure of nucleic acids.

In 1976, Crick took a sabbatical year at the Salk Institute for Biological Studies in La Jolla, California, having been a nonresident fellow of the Institute since 1960. He found Southern California congenial and stayed, eventually holding the post of J. W. Kieckhefer Distinguished Research Professor at the Salk Institute for the rest of his life. He taught himself neuroanatomy and spent several years disengaging from molecular biology before devoting his full attention to the problem of consciousness in the 1980s.

Crick was struck by how fragmented neuroscience was, with many subdisciplines working in isolation, and by the fact that consciousness was treated as a taboo subject by many neurobiologists. In 1983, Crick and Mitchison proposed that the function of REM sleep and dreaming is to remove certain unwanted patterns of interaction from networks of cells in the mammalian cerebral cortex — a process they called reverse learning or unlearning. From 1990 onwards, Crick developed a long collaboration with Christof Koch, producing a series of papers on the neural basis of visual awareness. He argued in his book The Astonishing Hypothesis that the mind is a product of physical brain activity and that neurobiology had reached a stage where consciousness could be studied at the molecular, cellular, and behavioural levels simultaneously.

Crick died of colon cancer on the morning of 28 July 2004 at the University of California, San Diego Thornton Hospital in La Jolla. According to Christof Koch, he was editing a manuscript on his death bed. A public memorial was held on 27 September 2004 at the Salk Institute, where speakers included Watson, Brenner, Koch, and other leading figures from neuroscience and molecular biology.