Gene Mutation, DNA Repair, and Transposition Chapter 14 Lecture Essentials of Genetics Gene Mutation, DNA Repair, and Transposition

14.1 Mutations Are Classified in Various Ways Spontaneous and Induced Mutations Classification Based on Location of Mutation Somatic Germline Autosomal X-linked Mutations are also classified as dominant versus recessive

14.1 Mutations Are Classified in Various Ways Classification Based on Phenotypic Effects Loss-of-function Gain-of-function Morphological Nutritional Behavioral Lethal Conditional

Classification Based on Type of Molecular Change Figure 15-1 Analogy of the effects of substitution, deletion, and insertion of one letter in a sentence composed of three-letter words, demonstrating point and frameshift mutations. Figure 15.1

14.2 Spontaneous Mutations Arise from Replication Errors and Base Modifications DNA Replication Errors Replication Slippage Tautomeric Shifts

Figure 15-2 Standard base-pairing relationships (a), compared with anomalous base-pairing that occurs as a result of tautomeric shifts (b). The long triangle indicates the point at which the base bonds to the pentose sugar. Figure 15.2

Figure 15-2a Standard base-pairing relationships (a), compared with anomalous base-pairing that occurs as a result of tautomeric shifts (b). The long triangle indicates the point at which the base bonds to the pentose sugar. Figure 15.2a

Figure 15-2b Standard base-pairing relationships (a), compared with anomalous base-pairing that occurs as a result of tautomeric shifts (b). The long triangle indicates the point at which the base bonds to the pentose sugar. Figure 15.2b

Figure 15-3 Formation of an A=T to G=C transition mutation as a result of a tautomeric shift in adenine. Figure 15.3

14.2 Spontaneous Mutations Arise from Replication Errors and Base Modifications Depurination and Deamination

Deamination Figure 15-4 Deamination of cytosine and adenine, leading to new base pairing and mutation. Cytosine is converted to uracil, which base pairs with adenine. Adenine is converted to hypoxanthine, which base pairs with cytosine. Figure 15.4

14.2 Spontaneous Mutations Arise from Replication Errors and Base Modifications Oxidative Damage Transposons

14.3 Induced Mutations Arise from DNA Damage Caused by Chemicals and Radiation Base Analogs: Compounds that can substitute for purines or pyrimidines during biosynthesis of amino acids.

15.3 Induced Mutations Arise from DNA Damage Caused by Chemicals and Radiation Alkylating Agents: Mustard gas is an example of an alkylating agent that adds alkyl groups to the purine or pyrimidine of the nucleotide.

Table -- Alkylating Agents crosslinks

Acridine Dyes and Frameshift Mutations Intercalating agents

Acridine Dyes and Frameshift Mutations Cause frameshift mutations. These agents form a wedge between purines and pyrimidines of intact DNA. This contorts the helix and can lead to deletions or insertions. Chemical structures of proflavin and acridine orange, which intercalate into DNA and cause frameshift mutations.

Ultraviolet Light Figure 15-7 Chemical structures of proflavin and acridine orange, which intercalate into DNA and cause frameshift mutations. Figure 15.7

Figure 15-8 The components of the electromagnetic spectrum and their associated wavelengths.

15.3 Induced Mutations Arise from DNA Damage Caused by Chemicals and Radiation Ionizing Radiation

Ionizing Radiation Figure 15-9 Plot of the percentage of X-linked recessive mutations induced by increasing doses of X rays. If extrapolated, the graph intersects the zero axis as shown by the dashed line. Figure 15.9