W9OutlineLec23 - functioning Nonsense-stop translation...

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Luis David Gomez Week 9 Lecture 23 Outline 59866865 Bio 192 D103 Cell Biology 3/3/08 Cell Cycle III--Genetics The fundamental core of the eukaryotic cell cycle control system - association of two classes of proteins, cyclins and cyclin-dependent kinases (Cdk), trigger key events during the cell cycle. Cyclin/CDK activity is held in check by a phosphtase—Wee1 Yeast—ideal organism for studying the cell cycle Easy to keep, maintain, grow FAST cell cycle Easy to mutagenize Haploid genoe—no diploid organisms because the extra copy of the chromosome will mask the mutations, therefore, haploid organisms are key Propagated in large quantitites Dominant mutation diploid shows phenotype Recessive mutation diploid no phenotype Dominant mutation haploid shows phenotype Recessive mutation haploid shows phenotype! How do you recover a haploid mutant then? Conditional Mutations—such as a Temperature Sensitive Mutation At a low temperature the mutation is permissive (functionable) At a higher temperature, the mutation is restrictive (non-
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Unformatted text preview: functioning) Nonsense-stop translation early b/c a mutation into stop codon Missense-subtle DNA change that causes a wrong amino acid to be incorporated during translation—most likely to give Ts mutation Frameshift —insert of 1 or 2 bases that makes a mutation that cause ribosome to start translating at different point Silent —a mutation occur that DNA is changed but A.A. stays the same Isolation Take a yeast culture add a mutagen incubate cells (grow them to allow a few cell cycles and allow expression of mutant proteins) plate out incubate on plates replicate the plate grow at two different temperatures\ Common ts mutants Wee 1—unable to stop cell division so that cells are tiny Cdc25—unable to undergo cell division so cells keep growing Compliment Rescue with Plasmids Add a wildtype copy of every gene into mutant yeast and see which one grows...
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