Chapter 17 outline - TheinformationcontentofDNAisintheform

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• The information content of DNA is in the form of specific sequences of nucleotides • The DNA inherited by an organism leads to specific traits by dictating the synthesis of proteins • Proteins are the links between genotype and phenotype •  Gene expression, the process by which  DNA directs protein synthesis, includes two stages: transcription and translation
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In 1909, British physician Archibald Garrod first  suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions George Beadle and Edward Tatum exposed bread mold to X-rays, creating mutants that were unable to survive on minimal medium as a result of inability to synthesize certain molecules They developed a  one   gene–one enzyme hypothesis, which states that each gene dictates production of a specific enzyme
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Some proteins aren’t enzymes, so  researchers later revised the hypothesis:  one gene–one protein • Many proteins are composed of several polypeptides, each of which has its own  gene •  Therefore, Beadle and Tatum’s  hypothesis is now restated as the  one gene–one polypeptide hypothesis • Note that it is common to refer to gene
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Basic Principles of Transcription and  Translation • RNA is the intermediate between genes  and the proteins for which they code •  Transcription is the synthesis of RNA  under the direction of DNA • Transcription produces  messenger RNA (mRNA) •  Translation is the synthesis of a  polypeptide,  which occurs under the  direction of mRNA •  Ribosomes are the sites of translation
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Chapter 17 outline - TheinformationcontentofDNAisintheform

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