10 - 2008 BIO320: Lecture 10 Mutation and fine structure...

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Luria and Delbruck demonstrated that mutations are pre-existing in a population of cells. Ruled out the idea of adaptive mutation which says that cells mutate in response to cues from the environment. GROW OVERNIGHT PLATE ON MEDIUM CONTAINING BACTERIOPHAGE. ONLY RESISTANT BACTERIA CAN GROW 1 20 2 30 1 200 Different numbers of resistant bacteria were observed depending upon when during the growth of the culture the mutation to phage resistance occurred. DILUTE BACTERIAL CELLS SO THAT THERE IS ONE PER TUBE Mutation and fine structure mapping. BIO320: Lecture 10 Chapter 7: 7-1, 7-2, 7-3, 7-6, 7-8, 7-14, 7-15 QB: L1-26. Mutation: heritable change in the DNA sequence--responsible for creating phenotypic variation There are two types of basepair substitutions : 5' G A T T C 3' 3' C T A A G 5' 5' G G T T C 3' 3' C C A A G 5' pyrimidine for pyrimidine purine for purine Transition mutation : purine replaces purine, pyrimidine replaces pyrimidine Transversion mutation: pyrimidine replaces purine; purine replaces pyrimidine The spontaneous mutation rate is very low due to processes such as mismatch correction and excision repair. Mutagens increase the spontaneous mutation rate. X-rays, ultraviolet light, base analogs, intercalators are different types of mutagens. 5' G
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10 - 2008 BIO320: Lecture 10 Mutation and fine structure...

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