Sum7LS4Week5b(1slide)

Sum7LS4Week5b(1slide) - Mutation and Gene Function Chapter...

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Mutation and Gene Function Chapter 13 Read pp. 344-363 Problems: 5, 7, 9, 15, 31, 39
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Mutations are the ultimate source of all genetic change
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Without mutations…
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Central Dogma transcription translation DNA RNA Protein
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Mutations are the ultimate source of all genetic change • Two major processes are responsible for genetic variation: 1) Mutation a change in the DNA sequence of a gene…results in the production of new alleles. 2) Recombination causes alleles of different genes to become grouped in new combinations.
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Mutations are the ultimate source of all genetic change Chromosome mutation : mutational events that affect the entire chromosome or large pieces of the chromosome. These affects will mainly result in gene dosage defects. Gene mutation : mutational events (changes in the DNA sequence) that take place within individual genes. These changes may or may not result in altering the spatial or functional state of the protein or the level of activity or specificity of the protein.
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Mutations can occur in either somatic cells or germ cells
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The Origin of Mutation Spontaneous mutation : arises naturally within the cell and are rare, random events. Are not caused by known mutagens. –Errors in DNA replication or repair –Loss of purine bases (As & Gs) –Conversions of Cytosine (C) to Uracil (U) –Insertions of transposable elements Induced mutation : arises through treatment with mutagens (agents/chemicals known to increase the rate of mutations. –High-energy radiation –Specific chemicals
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Mutations: Random & Nonadaptive • Max Delbruck and Salvador Luria: “fluctuation test”
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Mutations: Random & Nonadaptive • Luria and Delbruck: “fluctuation test” -Showed that in individual bacterial cultures, the numbers of mutants that arose in a given volume varied considerably from culture to culture, thus they must have occurred randomly in time.
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Experiment : Plate bacteria on non-selective master plate. Replica plate onto a series of plates containing high conc. of phage T1. Result : all replica plates had the same resistant colonies. Is mutation a response to selection? What does this result suggest?
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Mutation rates • For diploid organisms, mutation rate (frequency/gamete) is in the range of 1/100,000
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• To study mutation, mutagens are used to induce mutations in experiments because spontaneous mutations are rare. I can’t wait forever!
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