(6 of 10)
The Magical Code. Weird and wonderful as is the field of high-energy physics, it offers no more glittering opportunities than those now open to the geneticists, the virologists, the biochemists and others who have recently begun calling themselves molecular biologists. The objective of the molecular biologists is nothing less than to explain the inner chemical workings of living creatures. Every living cell, including those of multicelled animals such as man, has in its nucleus large and complicated molecules that control growth and heredity. Except in some bacteria and viruses, these molecules are made of deoxyribonucleic acid (DNA), which James Watson of Harvard and Francis Crick of Cambridge, England, found to be two long chains of atoms linked together and twisted spirally. The links between the two spirals, often many thousands of them, differ slightly and constitute a sort of code that carries information and controls the heredity of the cell.
When a cell reproduces by division, the DNA molecules in its nucleus have two jobs. First they must make perfect duplicates of themselves. Then they must control the formation of enzymes (protein catalysts) that will generate the other proteins that the cell needs to grow bigger and split in two.
The most direct way to achieve understanding of this system would be to find the exact structure of DNA, including the magical code. But when it is considered that the DNA molecules in human cells may have something like a million atoms all linked and twisted in a special way, the difficulties stagger imagination. So the attack on the molecules of life is mounted in other, more indirect ways. One approach is through genetics: learning about the chemistry of reproduction of small and comparatively simple organisms like molds. Another approach is through X-ray studies of proteins, with the X rays scattering in patterns and giving clues about protein structure. Using this technique, Cambridge's Dr. John Kendrew recently located a large part of the 2,500 coiled-up atoms in myoglobin, a rather simple protein. The size of the entire problem is suggested by the fact that most protein molecules are much bigger than myoglobin, and that there are about 100,000 different proteins in the human body.
Despite such chilling challenges, the molecular biologists have the tingling feeling that they are about to break through the black unknown. Caltech's Geneticist George Beadle thinks that future understanding of DNA and proteins may tell why some cells of a developing embryo turn into skin, others into bone or brain. Caltech's Pauling, a physical chemist who shifted to biochemistry and proved that proteins have a coiled structure, believes that "very fundamental discoveries are now possible in this field. The foundation has been laid for men to make a penetrating attack on the nature of life." With deeper understanding of the proteins and DNA of the human body, it should become possible to treat and correct genetic diseases, now mostly incurable. "Why," says Pauling, "we could increase the life expectancy of Americans by 20 years. I don't mean just keeping old people alive 20 years longer. We'd keep people in their youth and middle age for 20 more years, with their health still good."