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

Spontaneous Mutations

Genetics

17. Mutation, Repair, and Recombination

Spontaneous Mutations

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1:24 minutes

Problem 1c

Textbook Question

How do we know that DNA repair mechanisms detect and correct the majority of spontaneous and induced mutations?

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Understand that DNA repair mechanisms are essential for maintaining the integrity of the genome. These mechanisms are studied through experiments that measure mutation rates in cells with and without functional repair systems.

Review the concept of spontaneous and induced mutations. Spontaneous mutations occur naturally due to errors in DNA replication or chemical changes, while induced mutations are caused by external agents like radiation or chemicals.

Examine experimental evidence where researchers compare mutation rates in wild-type cells (with functional repair systems) to those in mutant cells lacking specific DNA repair pathways. A higher mutation rate in repair-deficient cells indicates the role of repair mechanisms in correcting errors.

Consider the use of mutagenic agents in experiments. Scientists expose cells to mutagens and then measure the frequency of mutations. They observe that cells with intact repair systems have significantly lower mutation rates compared to repair-deficient cells, demonstrating the effectiveness of repair mechanisms.

Analyze the molecular mechanisms of specific DNA repair pathways, such as base excision repair, nucleotide excision repair, and mismatch repair. These pathways are studied using biochemical assays and genetic analysis, which show how they detect and correct DNA damage, preventing mutations from becoming permanent.

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Key Concepts

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

DNA Repair Mechanisms

DNA repair mechanisms are cellular processes that identify and correct damage to the DNA molecules that encode an organism's genome. These mechanisms include various pathways such as base excision repair, nucleotide excision repair, and mismatch repair, which work to fix different types of DNA lesions. Understanding these processes is crucial for comprehending how cells maintain genetic integrity and prevent mutations.

Spontaneous and Induced Mutations

Spontaneous mutations occur naturally during DNA replication or due to internal cellular processes, while induced mutations result from external factors such as radiation or chemical exposure. Both types of mutations can lead to changes in the genetic code, potentially affecting protein function and cellular behavior. Recognizing the sources and types of mutations helps in understanding the necessity and effectiveness of DNA repair mechanisms.

Experimental Evidence for DNA Repair

Experimental evidence for the effectiveness of DNA repair mechanisms comes from various studies, including those using mutant strains of organisms that lack specific repair pathways. These studies often show increased mutation rates in these mutants compared to wild-type organisms, demonstrating that DNA repair systems are essential for correcting errors and maintaining genomic stability. Such evidence supports the conclusion that these mechanisms can detect and correct the majority of mutations.

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Related Practice

Textbook Question

Describe a tautomeric shift and how it may lead to a mutation.

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Textbook Question

The family of a sixth-grade boy in Palo Alto, California, was informed by school administrators that he would have to transfer out of his middle school because they believed his mutation of the CFTR gene, which does not produce any symptoms associated with cystic fibrosis, posed a risk to other students at the school who have cystic fibrosis. After missing 11 days of school, a settlement was reached to have the boy return to school. What ethical problems might you associate with this example?

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Textbook Question

What genetic defects result in the disorder xeroderma pigmentosum (XP) in humans? How do these defects create the phenotypes associated with the disorder?

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Textbook Question

Presented here are hypothetical findings from studies of heterokaryons formed from seven human xeroderma pigmentosum cell strains:

These data are measurements of the occurrence or nonoccurrence of unscheduled DNA synthesis in the fused heterokaryon. None of the strains alone shows any unscheduled DNA synthesis. Which strains fall into the same complementation groups? How many different groups are revealed based on these data? What can we conclude about the genetic basis of XP from these data?

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Multiple Choice

Which of the following results in a spontaneous mutation?

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Multiple Choice

Which of the following tests determined that most mutations are spontaneous?

True or False:Thymine tautomers can base pair with cytosine.