Lecture 15 - Transcription & Translation 10-29

Lecture 15 - Transcription & Translation 10-29 -...

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Unformatted text preview: From gene to gene product Principles of Biology Lecture 15 Prof. David Fitch 2007 D. Fitch Summary DNA is the basis for inheritance in most systems DNA structure primary sequence = information double helix and base complementarity = means of copying information DNA replicates semiconservatively DNA replication occurs 5'-to-3' this constraint imposes a problem in replicating the "lagging" strand DNA replication involves many components unwinding and opening of the replication fork at the origin(s) RNA primer elongation by DNA Pol III Okazaki fragments due to lagging strand synthesis removal of RNA primer and replacement with DNA by Pol I ligation of nascent DNA segments (DNA ligase) Model of DNA replication DNA replication in E. coli Leading strand Replication fork DNA pol III Primase Primer DNA pol III Lagging strand DNA pol I DNA ligase Parental DNA Primase 5 3 3 Helicase SSB Overall direction of replication The "Central Dogma" of molecular biology DNA RNA protein or nucleic acid protein and other gene products What is a gene? One gene one enzyme hypothesis Garrod (after consultation with William Bateson, a Mendelian, deduced by pedigree analysis that alkaptonuria was recessive (first description of a recessive trait in human) 1902. The Incidence of Alkaptonuria: a Study in Chemical Individuality . Also described cystinuria, pentosuria, and albinism as chemical deficiencies 1923. Inborn Errors of Metabolism QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. One gene - one enzyme Neurospora crassa auxotrophs (mutants defective in metabolism) What are the steps in arginine biosynthesis? George Beadle Edward Tatum QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. Quic kTime and a TIFF (Uncompres s ed) dec ompres sor are needed to s ee this pic ture. 1958 Metabolism mutants Minimal medium P as phosphate N as ammonium S as sulfate C as sugar Mg 2+ trace elements Rich medium same, but supplemented with all 20 amino acids Auxotroph mutant that requires an additional nutrient not required by the wild type Prototroph the wild type which gives rise to the auxotroph Mutants presumed to affect one locus different mutants isolated and characterized as auxotrophs for different amino acids allelic mutants "failed to complement" in crosses non-allelic mutants presumed to reflect different loci Complementation test QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture....
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Lecture 15 - Transcription & Translation 10-29 -...

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