One - Crossing the mutated fungi with non-mutated forms...

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One-gene-one-protein In 1941 Beadle and coworker Edward L. Tatum decided to examine step by step the chemical reactions in a pathway. They used Neurospora crassa as an experimental organism. It had a short life-cycle and was easily grown. Since it is haploid for much of its life cycle, mutations would be immediately expressed. The meiotic products could be easily inspected. Chromosome mapping studies on the organism facilitated their work. Neurospora can be grown on a minimal medium, and it's nutrition could be studied by its ability to metabolize sugars and other chemicals the scientist could add or delete from the mixture of the medium. It was able to synthesize all of the amino acids and other chemicals needed for it to grow, thus mutants in synthetic pathways would easily show up. X-rays induced mutations in Neurospora , and the mutated spores were placed on growth media enriched with all essential amino acids.
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Unformatted text preview: Crossing the mutated fungi with non-mutated forms produced spores which were then grown on media supplying only one of the 20 essential amino acids. If a spore lacked the ability to synthesize a particular amino acid, such as Pro (proline), it would only grow if the Proline was in the growth medium. Biosynthesis of amino acids (the building blocks of proteins) is a complex process with many chemical reactions mediated by enzymes, which if mutated would shut down the pathway, resulting in no-growth. Beadle and Tatum proposed the "one gene one enzyme " theory. One gene codes for the production of one protein. "One gene one enzyme" has since been modified to "one gene one polypeptide " since many proteins (such as hemoglobin) are made of more than one polypeptide....
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This note was uploaded on 11/29/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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One - Crossing the mutated fungi with non-mutated forms...

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