The Secret of Life

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A few sprouted hopefully but did not grow. These were the interesting spores. They acted as if they were trying to grow, but needed something that they could not get from the agar or produce for themselves. So when a microscope showed such a spore, it was tenderly fed with vitamins, amino acids and other growth-fostering chemicals in hope of making it perk up and grow normally.

At the start of the experiment, Beadle and Tatum resolved to make at least 1,000 tries before giving up. Such perseverence was not necessary. On the 299th try they found an ailing spore that needed only vitamin B-6 (pyridoxine) to make it grow lustily. When it had mated with a normal mold, it transmitted its need for vitamin B-6 to its descendants in the proper Mendelian manner for a single mutated gene.

This was what Beadle had been hoping for. His explanation is that the gene damaged by X-ray violence was originally responsible for producing an enzyme (organic catalyst) needed in the mold's process of making vitamin B-6 out of simpler nutrients. With the gene out of action, the process stopped, and the mold could not grow without help. It was like a human diabetic who needs an external source of the insulin that his body cannot make.

New Attitude. When Beadle and Tatum reported their success in 1941, they had quite a collection of defective molds, each needing some extra nutrient or having some other gene-controlled chemical ailment. In a few years their imitators filled their own laboratories with molds as unnatural as the most monstrous fruit flies. The coral fluffs of normal Neurospora are rare in the test tubes and Petri dishes. In their place are blackish warts, lichenlike incrustations, or sick-looking globules. One horrible kind of mold grown in a moving liquid floats in bunches with limp limbs like soft, dead crabs.

An immediate, practical result of Neurospora genetics was the application of mold irradiation to wartime penicillin production. Much more important were the long-range scientific results. The success with Neurospora yielded new techniques for using molds and other small organisms as genetic tools. Out of its use flowed a new attitude toward genetics. No longer were genes considered abstract units of heredity. They became actual things, not entirely understood but known to be concerned with definite chemical actions. Professor Joshua Lederberg, 33, of the University of Wisconsin, probably the world's leading young geneticist, says that the Neurospora work at Stanford clinched the whole idea that genes control enzymes, and enzymes control the chemistry of life.

In 1946 Caltech needed a new head for its now famous Division of Biology. Professor Morgan had retired. Beadle was tapped for the job and accepted, knowing well that he would have to curtail, perhaps abandon, his personal research. Some of his friends felt that a great scientist was being wasted on a routine administrative job, and there was a precedent for their fears in the history of genetics. Mendel himself did nothing of note after he was made abbot.