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

2. 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

3. 14.1 Mutations Are Classified in Various Ways
Classification Based on Phenotypic Effects
Loss-of-function
Gain-of-function
Morphological
Nutritional
Behavioral
Lethal
Conditional

4. 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

5. 14.2 Spontaneous Mutations Arise from Replication Errors and Base Modifications
DNA Replication Errors
Replication Slippage
Tautomeric Shifts

6. 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

7. 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

8. 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

9. 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

10. 14.2 Spontaneous Mutations Arise from Replication Errors and Base Modifications
Depurination and Deamination

11. 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

12. 14.2 Spontaneous Mutations Arise from Replication Errors and Base Modifications
Oxidative Damage
Transposons

13. 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.

14. 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.

15. Table -- Alkylating Agents
crosslinks

16. Acridine Dyes and Frameshift Mutations
Intercalating agents

17. 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.

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

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

20. 15.3 Induced Mutations Arise from DNA Damage Caused by Chemicals and Radiation
Ionizing Radiation

21. 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