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Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoSanders 3rd EditionCh. 11 - Gene Mutation, DNA Repair, and Homologous RecombinationProblema 34a
Capitolo 11, Problema 34a

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.
A change in DNA sequence caused by a mistake made by DNA polymerase during replication

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Step 1: Identify the type of DNA damage described in the problem. The damage is a change in the DNA sequence caused by a mistake made by DNA polymerase during replication. This type of error is typically referred to as a mismatch or replication error.
Step 2: Recall the DNA repair pathway responsible for fixing mismatches. The mismatch repair (MMR) pathway is specifically designed to correct errors introduced during DNA replication, such as base mismatches or small insertion/deletion loops.
Step 3: Understand the mechanism of the mismatch repair pathway. MMR detects the mismatch by recognizing distortions in the DNA helix caused by incorrect base pairing. It then excises the incorrect segment of DNA and replaces it with the correct sequence using the undamaged strand as a template.
Step 4: Explain why other repair pathways are not suitable for this type of damage. For example, nucleotide excision repair (NER) is used for bulky lesions like thymine dimers, and base excision repair (BER) is used for small, non-helix-distorting base modifications. Neither of these pathways is designed to address replication errors.
Step 5: Conclude that the mismatch repair pathway is the most appropriate mechanism for repairing the described DNA damage, as it specifically targets replication errors caused by DNA polymerase.

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DNA Replication

DNA replication is the process by which a cell duplicates its DNA before cell division. During this process, DNA polymerase synthesizes a new strand by adding nucleotides complementary to the template strand. However, errors can occur, leading to mismatches in the DNA sequence, which necessitate repair mechanisms to maintain genetic integrity.
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Steps to DNA Replication

DNA Repair Mechanisms

DNA repair mechanisms are cellular processes that correct damage to the DNA molecule. These mechanisms include various pathways such as base excision repair, nucleotide excision repair, and mismatch repair. Each pathway is specialized for different types of DNA damage, ensuring that errors introduced during replication or due to environmental factors are effectively repaired.
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Repair Pathways

Mismatch Repair Pathway

The mismatch repair pathway is a specific DNA repair mechanism that corrects errors made during DNA replication, particularly those involving base pair mismatches. This pathway identifies and removes incorrectly paired nucleotides, followed by resynthesis of the correct sequence by DNA polymerase. It plays a crucial role in maintaining genomic stability and preventing mutations.
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Repair Pathways
Pratica correlata
Domanda del libro di testo

In an experiment employing the methods of the Ames test, two strains of Salmonella are used. Strain A contains a base-substitution mutation, and Strain B contains a frameshift mutation. Four plates are prepared to test the mutagenicity of the compound ethyl methanesulfonate (EMS). Plate 1 is a control plate with Strain A and S9 extract but no EMS. Plate 2 is also a control plate and contains Strain B and S9 extract but no EMS. Plate 3 contains Strain A along with S9 extract and EMS, and Plate 4 contains Strain B, S9 extract, and EMS.

What event is being detected by growth of a colony on any of the four plates?

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Domanda del libro di testo

In an experiment employing the methods of the Ames test, two strains of Salmonella are used. Strain A contains a base-substitution mutation, and Strain B contains a frameshift mutation. Four plates are prepared to test the mutagenicity of the compound ethyl methanesulfonate (EMS). Plate 1 is a control plate with Strain A and S9 extract but no EMS. Plate 2 is also a control plate and contains Strain B and S9 extract but no EMS. Plate 3 contains Strain A along with S9 extract and EMS, and Plate 4 contains Strain B, S9 extract, and EMS.

Why is the S9 extract added to each of the plates?

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Domanda del libro di testo

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.

A double-strand break that occurs just after replication in an actively dividing cell

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Domanda del libro di testo

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.

Heavily damaged bacterial DNA

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Domanda del libro di testo

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.

A thymine dimer induced as a result of UV exposure

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Domanda del libro di testo

In an experiment employing the methods of the Ames test, two strains of Salmonella are used. Strain A contains a base-substitution mutation, and Strain B contains a frameshift mutation. Four plates are prepared to test the mutagenicity of the compound ethyl methanesulfonate (EMS). Plate 1 is a control plate with Strain A and S9 extract but no EMS. Plate 2 is also a control plate and contains Strain B and S9 extract but no EMS. Plate 3 contains Strain A along with S9 extract and EMS, and Plate 4 contains Strain B, S9 extract, and EMS.

Suppose the compound being tested was proflavin instead of EMS. Would this change the Ames test results? Explain why or why not.

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