"Almost all aspects of life are engineered at the molecular level, and without understanding molecules we can only have a very sketchy understanding of life itself."
As a theorist in a science based on experiment, Francis Crick, more than any other single scientist, defined the field of molecular biology during its "classical period" from the discovery of the double helical structure of deoxyribonucleic acid (DNA) in 1953 to the elucidation of the complete genetic code in 1966. In the words of fellow Nobel laureate Jacques Monod, "No one man discovered or created molecular biology. But one man dominates intellectually the whole field, because he knows the most and understands the most: Francis Crick." Crick went on to make important contributions to developmental biology and, during the last twenty-five years of his life, to neurobiology. His insights into DNA and the genetic code, ground-breaking in their time, have become standards of science education as well as references in popular culture.
Francis Harry Compton Crick was born on June 8, 1916, to middle-class parents in Northampton, England, a center of leather and footwear manufacturing. Crick's father managed a shoe and boot factory which his own father had founded. His mother was a school teacher.
In his autobiography, What Mad Pursuit (1988), Crick recounts that while a student at Northampton Grammar School he performed chemistry experiments, including a failed attempt to make artificial silk, but otherwise does "not recall being exceptionally precocious." At age fourteen he won a scholarship to Mill Hill School, a private boys' school in North London. Crick remembers that science instruction there was thorough, but still he learned the basics of Mendelian genetics on his own because it was not taught at the school.
Upon graduating from University College London in 1937 with a second-class honors degree in physics, he took up graduate work in physics at the college, studying the viscosity of water at high temperatures. These studies, which never engaged Crick intellectually, were interrupted by World War II when a bomb destroyed his apparatus. During the war he served on the scientific staff of the Admiralty, where he designed acoustic and magnetic mines for naval warfare.
In 1947, Crick, thirty-one years old, intellectually restless, weary of military research, and with an undistinguished record in his chosen field of physics, decided to change fields and careers altogether. In making this decision he applied what he called the "gossip test": he figured that the issues one feels most passionate for are those one gossips about, and that insight will come from the curiosity and dedication that only passion can sustain. Crick thus determined that he was faced with a choice between two scientific areas: molecular biology and the mysteries of consciousness. Concluding that his training in physics prepared him better for the former, Crick in 1947 successfully applied for a fellowship from the Medical Research Council (MRC), the agency that has general responsibility for the promotion of biomedical research in Britain.
Crick joined a cohort of physicists, including Max Delbrück, Leo Szilard, Maurice Wilkins, and Seymor Benzer, who turned to molecular biology in order to apply approaches central to physics (quantum mechanics, quantitative methods, and model building) to a science with few theoretical or mathematical underpinnings. Crick characterized the intellectual adjustment required by his transition from physics to biology "almost as if one had to be born again," because a theorist in biology had to rely on experimental evidence to a much greater extent than in physics. With little knowledge of biology, Crick went to Cambridge University to work at the Strangeways, a tissue culture laboratory where for two years he studied the physical properties of cytoplasm, the material of the cell that surrounds the nucleus, while reading widely in biology and chemistry.
In 1949, he transferred to the MRC's unit at the Cavendish physics laboratory in Cambridge. There he pursued doctoral research under Max Perutz on the determination of protein structure by X-ray crystallography, a technique by which crystals of molecules were exposed to X-rays, yielding a diffraction pattern on photographic film which allowed inferences about the position of the individual atoms within the molecule.
In the summer of 1951, Crick began his collaboration with James D. Watson, a postdoctoral fellow from the United States eleven years his junior. Their collaboration is the best-known of several examples of Crick's remarkable ability to form sustained productive friendships with other scientists. During long conversations in their shared office and at daily lunches at The Eagle, a pub around the corner from the Cavendish, the two delineated the physical structure of DNA, the molecule that had recently been shown to control heredity. They reported in the journal Nature on April 25, 1953, that DNA consisted of a double helix in which two sugar-phosphate backbones were linked like a twisted ladder by four types of nitrogen-containing bases, so that adenine was always paired with thymine and guanine with cytosine. The pairing rule meant that the two chains were complementary and that each could serve as a template for a new chain during cell division, providing a model for the transmission of hereditary characteristics from one generation to the next.
In recognition of their discovery Watson and Crick received the Nobel Prize in Physiology or Medicine in 1962 together with Maurice Wilkins, the crystallographer who had taken the first high-resolution X-ray images of DNA fibers and who had thus laid the groundwork for their discovery. Later Crick hung a helix, single-stranded and painted gold, over the door to the double-wide row house in the historic center of Cambridge he and his family occupied for many years.
Crick regarded the discovery of the double helix as a powerful example of the experimental and theoretical methods by which complex problems in biology could be reduced to fundamental laws of physics and chemistry. Indeed, throughout his scientific career he was driven by his conviction that the origins and processes of life, including human consciousness and free will, could be explained entirely in rational, scientific terms. In a series of lectures published under the title Of Molecules and Men (1966), he formulated his stance against what he called vitalism, the belief that life, evolution, and consciousness were generated and directed by a metaphysical force not subject to verification by experiment. An avowed atheist, Crick resigned as a fellow of Churchill College, Cambridge, after one year when the college decided to erect a chapel, which he considered an offensive anachronism.
Crick earned his PhD degree from Cambridge University's Gonville and Caius College in 1953, with a dissertation entitled "X-Ray Diffraction: Polypeptides and Proteins," in which he worked out the theory of X-ray diffraction by a helix. He spent the 1953-54 academic year as a postdoctoral researcher in the laboratory of the X-ray crystallographer David Harker at the Polytechnic Institute of Brooklyn, the first of many visits to the United States.
Upon returning to the MRC laboratory at Cambridge, his home institution for the next twenty-two years, Crick undertook research of rare breadth. (He never taught or advised students.) He renewed his collaboration with Watson in 1955, when the two developed a general theory about the molecular structure of small viruses, and he worked with the visiting American biochemist Alexander Rich on the structure of several biological molecules, particularly collagen, a family of proteins that are found outside of cells and that give strength and flexibility to connective tissue.
However, Crick devoted most of his efforts between 1954 and the mid-1960s to studying the genetic coding problem, that is, the action by which genes controlled the synthesis of proteins, the building blocks of life. Crick inferred that the sequence in which the four bases of DNA were arrayed encoded the instructions for building long chains made of a combination of the twenty common amino acids, which then folded themselves up into proteins. (Watson and Crick drew up the canonical list of twenty amino acids at The Eagle.) Crick called this inference the sequence hypothesis. The challenge was to decipher the code by which the four-letter language of DNA was translated into the twenty-letter language of proteins. In tackling the coding problem, Crick assumed that genetic information, once transmitted from DNA (probably through a messenger made, most likely, of ribonucleic acid, or RNA) and used to assemble the amino acid chain, could not reversely flow out of the protein and affect the sequence of the bases in the RNA messenger. This he proclaimed to be the "Central Dogma" of molecular biology. Finally, he predicted the existence of a group of molecules, later found and called transfer RNA, that aided in the assembly of the amino acid chain.
Crick began work on the genetic code with Vernon Ingram and continued it during his most enduring collaboration, that with the South African geneticist Sydney Brenner, from 1957 onward. In 1961, Crick and Brenner described in Nature how, by studying mutations in a bacterial virus, they obtained evidence that the genetic code was to be read three bases at a time, proceeding in one direction from a fixed starting point on the DNA strand. (The American biochemist Marshall Nirenberg had, concurrently, reached the same conclusion.) Over the next five years, Crick and his colleagues in England and the United States identified the triplets for all twenty amino acids in a rush of inspired research and friendly competition.
With the elucidation of the genetic code completed and molecular biology established on a firm footing, Crick in the mid-1960s turned to other fields, especially to developmental biology, the study of how genes control the growth and specialization of organs. To reflect this shift Crick and Brenner, who in 1962 had become joint heads of the Molecular Genetics Division of the Medical Research Council's newly-established Laboratory of Molecular Biology in Cambridge, renamed the division the Division of Cell Biology in 1969. During these years he was much in demand as a lecturer, a role in which he excelled and in which he traveled the globe.
In 1976, he began a sabbatical year at the Salk Institute for Biological Studies in La Jolla, California, a privately-funded research institute whose scientific direction Crick, as a Visiting Fellow, had helped to plot from the time it was built in 1962. In 1977, he accepted a permanent appointment there as J. W. Kieckhefer Research Professor. He used the occasion of his relocation to the United States to shift his focus from molecular biology to his other long-standing scientific interest, neurobiology. In further collaborations, notably with the computational neuroscientist Christof Koch, Crick studied the visual system of humans in an attempt to uncover the neural correlates of consciousness, how the electrochemical interactions of nerve cells in the cerebral cortex and related parts of the brain give rise to the subjective mind. He explained his approach to consciousness in The Astonishing Hypothesis: The Scientific Search for the Soul (1994), and published articles on such issues as the action of dendritic spines and the function of dream sleep. He was editing his latest article on neurobiology just days before his death from colon cancer on July 28, 2004, in La Jolla, California, at age eighty-eight.
Crick was elected a Fellow of the Royal Society in 1959, became a Foreign Associate of the U.S. National Academy of Sciences in 1968, and was a member of the French Academy of Sciences and the Irish Academy of Sciences. He received the Lasker Award, often called the American Nobel Prize, in 1960, with Watson and Wilkins. He also received the Award of Merit of the Gairdner Foundation of Canada, and the Prix Charles Leopold Mayer of the French Academy of Sciences, along with other important recognitions. In 1991, the Queen named Crick to the Order of Merit, an honorary institution of 24 outstanding scientists, artists, and writers. (Contrary to common assumption, he was never knighted.) Crick is the author of four books and more than 130 scientific articles.
Crick's first marriage, to Ruth Doreen Dodd, ended in divorce in 1947. He was survived by his wife, Odile, an artist whom he met at the Admiralty while she was serving as a translator of captured German documents, and whom he married in 1949; a son from his first marriage, Michael F. C. Crick, a software designer in Seattle; two daughters from his second marriage, Gabrielle A. Crick and Jacqueline M. T. Nichols, both of England; and six grandchildren.