The Secret of Life

Monday, Jul. 14, 1958
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Where did you come from, baby dear?

Out of the everywhere into the here.

Where did you get those eyes so blue?

Out of the sky as I came through.

—George MacDonald

The origin of baby dear, and the reasons for "eyes so blue" are the concern of genetics, the comparatively young, fast-developing science of heredity that is trying to solve the mystery of life, as physics works at solving the mystery of matter. Genetics has already accounted scientifically for blue eyes (even in a strictly dark-eyed family). It is working toward an explanation of how the first life appeared on earth. It is offering knowledge that may lead to the cure of cancer. And it came along just in time to warn against misuse of another young science: nuclear physics. The comparative "cleanness" (low fallout) of the test bombs that the U.S. was exploding in the Pacific last week was in large part a response to the warnings of the geneticists.

So young is the modern science of genetics that some of its grand old men are still alive, and some who gave it form are still only middleaged. Outstanding among them: Professor George Wells Beadle of Caltech, who did most to put modern genetics on its chemical basis. Geneticist Beadle is a mere 54. In his working lifetime he has seen genetics grow from a small, rather baffled specialty into a central, exciting science that is drawing the rapt attention of chemists, physicists, mathematicians, even astronomers, as well as nearly every type of biologist.

Monk & Peas. Genetics got its recognizable start, along with relativity, quantum theory and nuclear physics, during the scientific revolution of the early 1900s, but it had a strange, unpublicized start more than 40 years earlier when Gregor Mendel, an Augustinian monk and natural-history teacher in Brünn (now Brno, Czechoslovakia), began experimenting with peas in the monastery garden. Mendel found that the parent plants transmitted their characteristics to their descendants in a predictable, mathematical way. When purebred red-flowered peas, for instance, are crossed with white-flowered ones, all the seeds grow into plants with red flowers. But when these red hybrid plants are crossed with each other, one-fourth of their offspring bear white flowers.

Mendel concluded that the reproductive cells of peas contain factors (now called genes) of two kinds: dominant and recessive. The gene for red-floweredness is dominant; the gene for white-floweredness is recessive. When red-and white-flowered plants are mated, the seeds produced get both genes, but the dominant red gene suppresses the recessive white gene. Result: red flowers in the first generation (see diagram).

The white-flowered gene, though suppressed, is still in existence. When red hybrid flowers are mated together, each seed in the second generation has a one-in-four chance of inheriting nothing but white-flowered genes. It will then bear white flowers, just as if its parents were of pure, white-flowered stock.* The other three-fourths of the seeds will bear red flowers.