Test_TranscriptionTranslation - Bio Test Transcription...

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Textbook : DNA inherited by an organism leads to specific traits by dictating the synthesis of proteins and of RNA molecules involved in protein synthesis Gene Expression – Process by which DNA directs the synthesis of proteins 17.1 – Genes specify proteins via transcription and translation Archibald Garrod (1909): - Suggested genes dictated phenotypes through enzymes that catalyze specific chemical reactions in the cell - Symptoms of an inherited disorder reflect a person’s inability to make a particular enzyme *Ex: Alkaptonuria (urine turns black because it contains alkapton) *Garrod said that most people have an enzyme that metabolizes alkapton *People with the disease inherited an inability to make that enzyme George Beadle & Boris Ephrussi (1960s): - In Drosophila, each of the mutations affecting eye color blocks pigment synthesis at a specific step by preventing production of the enzyme that catalyzes that step George Beadle & Edward Tatum: - Worked with bread mold ( Neurospora crassa) - Bombarded mold with X-rays (known to cause genetic changes) and looked among the survivors for mutants that differed in nutritional needs from the wild type *WT minimal medium *Synthesize everything else needed - Identified mutants that couldn’t survive w/ minimal medium (couldn’t synthesize essential molecules) and let them grow on complete growth medium (20 aa & nutrients) - Wanted to characterize metabolic defect in mutants *Took samples from the mutants and placed them in a vial contained minimal medium and 1 additional amino acid *Supplement that allowed the mutant to live = metabolic defect - Each mutant was defective in a single gene supported one gene-one enzyme hypothesis *Function of a gene is to dictate the production of an enzyme Revisions made to one gene-one enzyme hypothesis: - Not all proteins are enzymes, but they are still gene products - Began to think one gene-one protein *Many proteins are constructed from 2 or more different polypeptide chains and each polypeptide is coded by its own gene ^Ex: Hemoglobin - Began to think one gene-one polypeptide *Many eukaryotic genes can code for a set of closely related polypeptides (alternative splicing) *Some genes code for RNA molecules that have important functions in cells even though they are never translated Basics of Transcription and Translation - Transcription = synthesis of RNA under the direction of DNA - DNA serves as a template for assembling a complementary sequence of RNA nucleotides (mRNA) - mRNA carries a genetic message from the DNA to the ribosomes - Translation = synthesis of polypeptide which occurs under direction of RNA - Cell must translate the base sequence of an mRNA molecule into amino acid sequence of polypeptide
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Test_TranscriptionTranslation - Bio Test Transcription...

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