Word: vitamine
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Beadle and Tatum irradiated masses of mold with X rays and searched for mutations in the spores. On the 299th try they got a mold that would not grow unless it was fed vitamin B-6 (pyridoxine). The normal mold makes vitamin B-6 for itself. They traced this deficiency to an X-ray-damaged gene that failed to produce the necessary enzyme (organic catalyst) for producing B6. This provided a means of studying genetic changes by corresponding changes in the organism's ability or failure to produce specific chemicals-thus giving genetics a new exactness and turning...
...Isoniazid, wonder drug of 1952 against TB, may set off inflammation of the peripheral nerves, causing phantom sensations, numbness, burning pain and weakness. Unless caught early and treated with vitamin B6, this neuritis becomes permanent...
...also grows nonsexually, so a truckload of mold with the same heredity can be grown, if desirable, from a single spore. But the best thing about Neurospora is that it asks for so little. It thrives on a medium containing nothing but mineral salts, sugar and a single vitamin, biotin. Everything else that it needs it can make out of these simple foods...
...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...