This document discusses gene mutation and DNA repair. It defines mutation as a heritable change in genetic material, which can be caused by spontaneous or induced events. Spontaneous mutations arise from errors in DNA replication, while induced mutations are caused by environmental mutagens. The main types of mutations are point mutations, insertions, deletions, and chromosomal rearrangements. Mutations can occur in germ-line or somatic cells and affect the genotype and phenotype in various ways. Organisms have developed DNA repair mechanisms to correct mutations but some mutations still occur.

1. Genetics: Analysis and Principles Robert J. Brooker Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display CHAPTER 16 GENE MUTION AND DNA REPAIR

8. 16-8

12. 16-11

14. 16-13

16. 16-15

20. Figure 16.2 16-20 Regulatory sequences are often bidirectional

22. Figure 16.4 16-22 Therefore, the mutation can be passed on to future generations The size of the patch will depend on the timing of the mutation The earlier the mutation, the larger the patch An individual who has somatic regions that are genotypically different from each other is called a genetic mosaic Therefore, the mutation cannot be passed on to future generations

24. 16-24

28. Test of the two hypotheses: Fluctuation Test Predictions:

30. 16-27 E.. coli is grown in the absence of T1 phages 20 million cells each 20 million cells each Many ton r bacteria Mutation occurred at an early stage of population growth, before T1 exposure No ton r bacteria Spontaneous mutation did not occur Several independent ton r mutations occurred during different stages These are mixed together in a big flask to give an average value of ton r cells Great fluctuation in the number of ton r colonies Relatively even distribution of ton r colonies The Luria-Delbruck fluctuation test Figure 16.6

33. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 16-32 Figure 6.20 Contain many mutations at exactly the same site within the gene

37. 16-36 Three out of four (A, T and G) are the incorrect nucleotide There’s a 75% chance of a mutation Spontaneous depurination Figure 16.8

41. 16-40 Figure 16.10 Rare Common

42. 16-41 Figure 16.10

43. 16-42 Figure 16.10 Temporary tautomeric shift Shifted back to its normal form

45. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 16-53

48. 16-56 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display These mispairings create mutations in the newly replicated strand Mispairing of modified bases Figure 16.13

51. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 16-59 Figure 16.14 In this way, 5-bromouracil can promote a change of an AT base pair into a GC base pair

55. 16-63 Provides a mixture of enzymes that may activate a mutagen The control plate indicates that there is a low level of spontaneous mutation The Ames test for mutagenicity Figure 16.16

57. 16-65

59. 16-67 Direct repair of damaged bases in DNA Figure 16.17

61. 16-69 Figure 16.18 Depending on whether a purine or pyrimidine is removed, this creates an ap urinic and an ap yrimidinic site, respectively Nick replication would be a more accurate term

64. 16-72 Figure 16.19

65. 16-73 Figure 16.19 Typically, the cuts are 4-5 nucleotides from the 3’ end of the damage, and 8 nucleotides from the 5’ end

70. 16-78 Acts as a linker between MutS and MutH Methyl-directed mismatch repair in E. coli Figure 16.21

71. 16-79 Methyl-directed mismatch repair in E. coli Figure 16.21

73. 16-81 Figure 16.22

74. 16-82 Figure 16.22

77. 16-85 Figure 16.24

79. * Ataxia telangiectasia * Bloom syndrome * Cockayne's syndrome * Progeria (Hutchinson-Gilford Progeria syndrome) * Rothmund-Thomson syndrome * Trichothiodystrophy * Werner syndrome * Xeroderma pigmentosum Human diseases due to mutations in genes involved in DNA repair

80. End of Chapter 16