How Genes Work

How Genes Work - Chapter 15: How Genes Work The science of...

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Chapter 15: How Genes Work The science of molecular biology began with the discovery that DNA is the hereditary material and that DNA is a double-helical structure containing sequences of four bases. I. What Do Genes Do? Creating knock out mutant alleles and analyzing their effects is still one of the most common research strategies in studies of gene function. a.The One-Gene, One-Enzyme Hypothesis i. Beadle and Tatum exposed a large number of N. crassa to radiation. High energy radiation damages the double helix and makes the gene nonfunctional. ii. One of the mutants could not make pyridoxine. This showed that due a single defect in a gene causes the inability to synthesize other molecules. iii. One-gene, one-enzyme hypothesis claimed that each gene contains the information needed to make an enzyme. b.An Experiment Test of the Hypothesis i. Biologists understand that genes contain instruction for making proteins. ii. Srb and Horowitz began raising colonies of irradiated cells on a medium that included argentine. Then they transferred a sample of N. crassa to a colony that lacked argenine. iii. Some mutants were able to grow on some media but not others. iv. This supported the idea that a gene affects an enzyme. II. The Central Dogma of Molecular Biology a.The Genetic Code Hypothesis i. Crick proposed that different combinations of bases could specify the 20 amino acids, just as different combinations of dots and dashes specify the 26 letters of the alphabet. A particular stretch of DNA could contain the information needed to produce the amino acid sequence of a particular enzyme. ii.
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How Genes Work - Chapter 15: How Genes Work The science of...

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