Chapter 15

Chapter 15 - Chapter 15 377 393 DNA Mutation I Mutation...

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I. Mutation – major source of genetic variation A. chromosomal mutations: change whole chromosomes or sections of them B. genetic mutations: affect function of genes; can alter phenotype by changing function of protein 2. point mutation: a change of 1 or a few bp; won’t change phenotype unless w/in gene or in sequences regulating the gene 3. transposable elements – transpose from 1 location to another in a genome II. Adaptation vs. Mutation A. Mutation theory – variation amng organisms resulted from random mutations that happened to be adaptive B. Lamarckism – doctrine of inheritance of acquired characteristics C. Experiment 2. Lamarckians argued that resistance trait of w.t. E. coli arose as a result of virulent T1 bacteriophage presence 3. others argued that mutations occur randomly, so that at any time in a large enough pop of cells, some cells have undergone a mutation that makes them resistant to T1 4. fluctuation test – showed mutation theory to be correct; if Lamarckian theory was correct, proportion of cells w/ adaptation would the same III. Mutation – process by which seq of bps in DNA molecule is altered A. can have somatic mutations (affects only the individual) or germ-line mutations (affects generations to come) B. mutation rate – probability of a particular kind of mutation as a function of time 2. mutation frequency - # of occurrences of a particular kind of mutation expressed as proportion of cells in a population 3. Point mutations – change 1 or a few bps c. bp substitution – 1 bp replaced by another i. transition mutation – one P-Y to the other P-Y ii. transversion mutation – one P-Y to Y-P (can be same or different) iii. mutation effects missense: change from 1 aa to another nonsense – change from aa to stop codon neutral – change from 1 aa to another aa w/ similar chemical properties silent – change in codon so that same aa is specified d. bp insertion/deletion i. frameshift effect – insertion/deletion changes reading frame c. effect of point mutations on phenotype i. forward mutation – changes genotype from w.t. to mutant ii. reverse mutations – changes genotype from mutant to w.t. or partially w.t. true reversion – actual changing back of original forward
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This note was uploaded on 02/09/2010 for the course BIOL 3301 taught by Professor Hannig/miller during the Spring '10 term at Dallas.

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Chapter 15 - Chapter 15 377 393 DNA Mutation I Mutation...

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