chapter 10

chapter 10 - Chapter 10 GENE EXPRESSION AND REGULATION DNA...

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Chapter 10 GENE EXPRESSION AND REGULATION
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DNA is the instructions (program) that tells the cell what to do. Proteins are the results of those instructions. The study of metabolic defects provided evidence that genes lead to proteins.
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This relationship was first proposed by Archibald Garrod in 1909 -suggested that some metabolic disorders were caused by a blocked pathway. -inherited diseases were the result of the lack of an enzyme
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ornithine enzyme 1 gene B gene A enzyme 2 arginine amino acid needed in protein synthesis citrulline The biochemical pathway for synthesis of the amino acid arginine involves two steps, each catalyze by a different enzyme. A blockage in a pathway not only stops the production of something we need but it also may lead to the accumulation of something we don’t want.
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George Beadle and Edward Tatum conducted experiment with bread mold, Neurospora crassa , and demonstrated that different mutants (generated by X- rays) had the pathway of arginine (an amino acid) synthesis blocked at different steps. The suggestions of Garrod were confirmed in the 1930's
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Minimal medium (MM) MM + ornithine MM + citrulline MM + arginine Wild type + + + + Mutant type I - + + + Mutant type II - - + + Mutant type III - - - + + = growth, - = no growth
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From these results they formulated the one gene-one enzyme hypothesis that was later clarified to “one gene one protein” Beadle and Tatum deduced that each of the 3 different mutant types lacked a different enzyme in the pathway which synthesizes arginine.
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DNA ==> RNA ==> Proteins
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Step one - DNA to RNA This process is called transcription . ---Transcription is the synthesis of RNA using DNA as a template
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-The RNA is complementary to the DNA -RNA that is synthesized from a gene coding for a protein is called messenger RNA (mRNA)
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2. base - thymine (DNA) is replaced by uracil (RNA)
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(template strand) of the DNA’s two strands is read. Different genes use
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chapter 10 - Chapter 10 GENE EXPRESSION AND REGULATION DNA...

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