Textbook Question
Outline the current model for DNA synthesis.
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Ch. 10 - DNA Replication
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Chapter 10, Problem 20a
Several temperature-sensitive mutant strains of E. coli display the following characteristics. Predict what enzyme or function is being affected by each mutation.
Newly synthesized DNA contains many mismatched base pairs.
Verified step by step guidance1
Understand the problem: The question describes a temperature-sensitive mutant strain of E. coli where newly synthesized DNA contains many mismatched base pairs. This suggests a defect in a process that normally ensures DNA replication fidelity.
Recall the key enzymes and functions involved in DNA replication and repair: DNA polymerase synthesizes new DNA strands, but it also has proofreading activity to correct mismatches. Additionally, mismatch repair enzymes correct errors that escape proofreading.
Analyze the phenotype: Since many mismatched base pairs remain in the newly synthesized DNA, the mutation likely affects either the proofreading function of DNA polymerase or the mismatch repair system.
Identify the specific enzyme or function: The proofreading activity is typically associated with the 3' to 5' exonuclease activity of DNA polymerase III in E. coli. If this activity is impaired, mismatches are not corrected during replication.
Conclude that the mutation probably affects the proofreading exonuclease activity of DNA polymerase III or the mismatch repair enzymes, leading to accumulation of mismatches in the DNA.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Replication Fidelity
DNA replication fidelity refers to the accuracy with which DNA polymerase copies the genetic material. High fidelity is maintained through correct base pairing and proofreading activities, ensuring minimal errors during replication.
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Steps to DNA Replication
Proofreading Activity of DNA Polymerase
Proofreading is a 3' to 5' exonuclease function of DNA polymerase that removes incorrectly paired nucleotides immediately after they are added. This activity significantly reduces replication errors by correcting mismatches before DNA synthesis continues.
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01:45DNA Proofreading
Mismatch Repair System
The mismatch repair system detects and repairs base-pair mismatches that escape proofreading after DNA replication. It enhances genomic stability by correcting errors that would otherwise lead to mutations.
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05:44Repair Pathways
Related Practice
Textbook Question
Several temperature-sensitive mutant strains of E. coli display the following characteristics. Predict what enzyme or function is being affected by each mutation.
Okazaki fragments accumulate, and DNA synthesis is never completed.
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Textbook Question
Define and indicate the significance of
(a) Okazaki fragments,
(b) DNA ligase, and
(c) primer RNA during DNA replication.
Textbook Question
Several temperature-sensitive mutant strains of E. coli display the following characteristics. Predict what enzyme or function is being affected by each mutation.
Synthesis is very slow.
Textbook Question
Why is DNA synthesis expected to be more complex in eukaryotes than in bacteria? How is DNA synthesis similar in the two types of organisms?
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Textbook Question
Several temperature-sensitive mutant strains of E. coli display the following characteristics. Predict what enzyme or function is being affected by each mutation.
No initiation occurs.