Chapter_17_Outline - Ch. 17: From Gene to Protein I. The...

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Ch. 17: From Gene to Protein I. The Connection between Genes and Proteins A. Dwarf peas have shorter stems than tall varieties because they lack growth hormones called gibberellins, which stimulate the normal elongation of stems. The dwarf peas cannot make their own gibberellins because they are missing a key protein, an enzyme required for gibberellin synthesis. B. Archibald Garrod first suggested that genes dictate phenotypes through enzymes by postulating that the symptoms of an inherited disease reflect a person’s inability to make a particular enzyme. C. Beadle and Tatum experimented with Neurospora with X-rays and then looked among the survivors for mutants that differed from the wild-type mold in their nutritional needs. They then identified mutants that could not survive on minimal medium and characterized the metabolic defect in each nutritional mutant. Their results provided strong support for the one gene-one enzyme hypothesis and showed how a combination of genetics and biochemistry could be used to work out the steps in a metabolic pathway. D. The one gene-one enzyme hypothesis stated that the function of a gene is to dictate the production of a specific enzyme; the one gene-one polypeptide hypothesis states that the function of a gene is to dictate the production of a specific polypeptide. The original hypothesis was changed because not all proteins are enzymes, and many proteins are constructed from two or more different polypeptide chains. E. RNA differs from DNA in that it contains ribose instead of deoxyribose as its sugar and has the nitrogenous base uracil rather than thymine. F. Information flows from gene to protein through transcription, the synthesis of RNA under the direction of DNA, and translation, the synthesis of a polypeptide, which occurs under the direction of mRNA. G. Transcription is the general term for the synthesis of any kind of RNA on a DNA template, while translation is the synthesis of a polypeptide. H. Transcription and translation are separated by the nuclear envelope, which transcription occurring in the nucleus and translation occurring in the cytoplasm of eukaryotes. In prokaryotes, transcription and translation occur simultaneously, with ribosomes attaching to the leading end of an mRNA molecule
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This note was uploaded on 06/15/2010 for the course FDST 4080 taught by Professor Pegg during the Spring '10 term at University of Georgia Athens.

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Chapter_17_Outline - Ch. 17: From Gene to Protein I. The...

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