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Biol notes - Title Gene Expression I Information in Cells A...

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Title: Gene Expression I. Information in Cells A. Central Dogma of Molecular Biology (CDMB) -is this a proclamation without proof? -NO -What does it mean? -A brief description of most important overall concept of molecular biology -What is this all about? -Information Flow within cells 1. Original Statement -DNA codes for RNA which codes for Protein - replication DNA transcription RNA translation Protein in nucleus of eukaryote in nucleus of in cytoplasm of eukaryote eukaryote -DNA stores information and is replicated -RNA contains information in DNA -RNA is used to direct synthesis of proteins 2. Modern Version -A more modern version is : DNA Reverse transcription RNA Protein -Adds additional step that DNA can be made from RNA through reverse transcription 3. Gene Expression -Central dogma describes flow of information -actual process is called gene expression: how genotype is converted into phenotype -involves process of -transcription -translation - Figure 15.2 -FIX FIGURE IN BOOK -T should be U on 5’ 3’ mRNA B. Genes and Proteins 1. Beadle and Tatum: Biochemical pathways -First clue for relationship came from Beadle and Tatum: -studied synthesis of arginine in Neurospora
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(1930’s and ‘40’s. Received Nobel prize in 1958) - Figure 15.1 -Beadle and Tatum screened four mutants that could not grow on minimal medium (simple solution containing carbon, and nitrogen sources, salts and biotin). -Once a mutant that could not grow on minimal medium was identified, the nutrient that restores growth (ex. Arginine) could be determined -Isolate mutant alleles of genes -Correlate with biochemical pathway -Mutants identified by failure to make Arg -Call this kind of mutant auxotroph (can’t make certain nutrient; requires outside source of nutrient for growth) -Supplement media with arg= growth -No supplement media with arg= no growth -Supplement with intermediates to determine pathway 2. Beadle and Tatum: Data -Ornithine and citrulline Z: the putative precursors of arginine -Growth Experiment Media supplement Mutant Ornithine Citrulline Arginine Wild type + + + Mutant E + + + Mutant F - + + Mutant G - - - E F G Glutamate precursor ornithine citrulline arginine -Conclusions? -Supplement with intermediate after block in pathway= growth -can dissect pathways using genetics 3. Interpretation: “One Gene, One Polypeptide” -Beadle and Tatum concluded each gene encoded a single enzyme in the pathway -one gene-one enzyme -one gene one polypeptide is better, because a particular enzyme may be made of multiple polypeptides -One gene may code for multiple polypeptides if alternative splicing occurs - Figure 15.1 II. Genetic Code A. Overview -need to understand the informatics of gene expression -relate information in DNA to info, in protein -the Genetic Code -cracking the code was a milestone of 20 th century biology -Combination of genetics, biochemistry, and organic chemistry B. Deciphering the Code 1. How Many Bases?
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Biol notes - Title Gene Expression I Information in Cells A...

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