Science: The Secret of Life

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But Beadle was not wasted. Since becoming chief of Caltech's biologists, he has revealed unexpected talents, including fund raising and speechmaking. His colleagues agree that his greatest talent is his way of encouraging and enhancing his division without visibly running it. He tries to function as a catalyst rather than as organizer, encouraging scientists from different disciplines to take a lively interest in each other's fields. Caltech's Division of Biology is equal to any in the world, and it operates in an atmosphere of amiability spiced with high intellectual excitement. These are Beadle's personal qualities, and he makes them infectious.

Morgan's House. In 1953 Beadle married young, handsome Muriel Barnett, a feature writer who still works at her newspaper job on the Los Angeles Mirror-News. She has a teen-age son, Redmond Barnett, whom Beadle has legally adopted. They live on Pasadena's San Pasqual Street near the Caltech campus in a charming, rambling house that once belonged to Dr. Morgan and was sold by his widow to Caltech. The grounds glow with flowers, some of them experiments in genetics but still attractive, and a patrol of eight Siamese cats keeps watch on everything interesting. Beadle is fond of all cats, but Siamese cats are his favorites. He explains that they would be dark all over except for a mutated gene that permits dark pigments to be formed only in places (ears, tail, nose, etc.) that have a low temperature.

Magic DMA. Since the Neurospora breakthrough, chemical genetics has made startling progress. Its most important movement has been down the scale of size toward the actual chemical molecules that control life and reproduction.

Never far from the geneticist's mind is the three-letter symbol DNA, which stands for deoxyribonucleic acid. It is a giant molecule of slightly variable composition that is found in chromosomes, and it is believed to be the substance that determines heredity and governs all cells (and therefore all life) from the stronghold of the nucleus. DNA has been known to exist for years, but until postwar years little was known about it. Now it is being attacked from many angles by nearly every breed of scientist.

In 1953 Caltech's Chemist Linus Pauling, who won a Nobel Prize for his work on molecular structure, reported that the DNA molecule has a helical (spiral-staircase) structure. Later that year, James D. Watson and Francis H.C. Crick in England went a step farther. DNA, they said, is a double helix with two spirally rising chains of linked atomic groups and a series of horizontal members, like steps, connecting the two spirals. This molecular model, deduced mostly from X-ray diffraction photos, seemed complex and unlikely, but geneticists rejoiced when they heard about it. It was just what they" needed to explain many perplexing things that they had been observing for years (see diagram).

In the Watson-Crick model of DNA, the two spirals are made of five-carbon sugar molecules (deoxyribose), alternating with phosphate groups. The "steps" connecting the two spirals are made of four "bases" (adenine, guanine, thymine, cytosine) linked in pairs. The pairs can point in either direction, but adenine must always be joined to thymine and guanine to cytosine.