Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

17. Mutation, Repair, and Recombination

Induced Mutations

Genetics

17. Mutation, Repair, and Recombination

Induced Mutations

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2:16 minutes

Problem 6b

Textbook Question

Ultraviolet (UV) radiation is mutagenic.
How do UV-induced DNA lesions lead to mutation?

Verified step by step guidance

Understand the nature of UV radiation: UV radiation is a form of electromagnetic radiation with wavelengths shorter than visible light. It is capable of causing damage to DNA by inducing chemical changes in the nucleotide bases.

Learn about UV-induced DNA lesions: UV radiation primarily causes the formation of pyrimidine dimers, such as thymine-thymine dimers or cytosine-thymine dimers. These lesions occur when adjacent pyrimidine bases on the same DNA strand become covalently bonded.

Explore the consequences of pyrimidine dimers: Pyrimidine dimers distort the DNA double helix structure, interfering with normal DNA replication and transcription processes. This can lead to errors during DNA synthesis.

Understand how mutations arise: If the DNA repair mechanisms, such as nucleotide excision repair, fail to correct the UV-induced lesions, DNA polymerase may insert incorrect bases opposite the damaged site during replication. This results in permanent changes to the DNA sequence, known as mutations.

Connect to broader implications: Mutations caused by UV radiation can lead to various outcomes, including cell death, malfunction, or uncontrolled cell growth (e.g., cancer). This highlights the importance of DNA repair systems in maintaining genomic integrity.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

UV Radiation and DNA Damage

Ultraviolet (UV) radiation can cause direct damage to DNA by inducing the formation of pyrimidine dimers, primarily thymine dimers. These dimers result from covalent bonding between adjacent thymine bases, disrupting the normal base pairing and leading to distortions in the DNA structure. If not repaired, these lesions can interfere with DNA replication and transcription.

DNA Repair Mechanisms

Cells have evolved several DNA repair mechanisms to correct UV-induced lesions, including nucleotide excision repair (NER) and photoreactivation. NER removes damaged sections of DNA and synthesizes new DNA to fill the gap, while photoreactivation directly reverses thymine dimers using light energy. Failure or inefficiency in these repair processes can lead to permanent mutations.

Mutation and Its Consequences

A mutation is a permanent alteration in the DNA sequence that can arise from unrepaired lesions. These mutations can lead to changes in protein function, potentially resulting in harmful effects such as cancer or genetic disorders. Understanding how UV-induced mutations occur is crucial for studying the mechanisms of carcinogenesis and the importance of DNA repair in maintaining genomic stability.

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