Chapter 17 SG - Chapter 17 Archibald Garrod-1st to suggest...

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Chapter 17 Archibald Garrod-1 st to suggest that genes dictate phenotypes through enzymatic catalysis; used alkaptonuria, which turned urine black due to a lack of the enzyme that normally breaks down alkapton; proven later from his time Beadle & Tatum- worked with bread mold neurospora using x-rays to detect survivors and what nutrients those needed a. Minimal medium- agar with inorganic salts, glucose and biotin survival confirms that mold is wild-type/efficient b. Complete Growth Medium- min medium + all 20 amino acids allows mutants to survive as well c. Characterization of defect involved taking survivors from complete medium and inserting each into different vials of different amino acids; those that did not grow confirms which amino acid cannot be broken down (defective gene) d. Arginine- amino acid that had 3 “stages” starting with a precursor nutrient ornithine citrulline arginine e. Results revealed 3 mutants for each amino acid “stage” implying that each mutant was defective in single gene, creating the one gene—one enzyme hypothesis , meaning that function of gene is to dictate making of specific enzyme One Gene–One Polypeptide Hypothesis- modification of Beadle & Tatum’s One Gene-One Enzyme hypothesis a. Protein Synthesis- keratin and insulin hormone are produced by genes but are not enymes b. Polypetide Synthesis- hemoglobin protein is made by 2 polypeptides, each requiring its own gene c. Hypothesis Evolution : enzyme (general) protein (broad) polypetide hypothesis (specific) Triplet Code- genetic instructions for polypeptide are written in DNA as series of three-nucleotide words Template Strand- only one of DNA’s two strands is transcribed into the pre-mRNA later processed and translated to the polypeptide Marshall Nirenberg- synthesized artificial RNA strand using Uracil (UUU) and placed in test tube with ribosomes amino acid Phe Reading Frame- correctly reading symbols in a series of non-overlapping 3-letter words AUG- has dual function as the start codon and amino acid Methionine; polypeptides have AUG to start, but is removed by enzyme Transcription- synthesis of RNA, specifically messenger RNA, under direction of DNA (DNA mRNA) Initiation- requires binding of RNA Pol II with trans-factors and TATA Box to the promoter starting transcription (1 st phase) RNA Polymerase II- opens DNA and places RNA complements synthesizing (pre)mRNA; don’t need primers and follows 5 3 Transcription Unit- stretch of DNA that is transcribed into RNA molecule Transcription Factors- in eukaryotes, mediates the binding of RNA pol to promoter, making the transcription initiation complex Promoter- where RNA Pol attaches and
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This note was uploaded on 08/27/2010 for the course BIO 8432 taught by Professor Lang during the Spring '10 term at Northwestern IA.

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Chapter 17 SG - Chapter 17 Archibald Garrod-1st to suggest...

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