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.
Newly synthesized DNA contains many mismatched base pairs.
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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 20d
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.
Verified step by step guidance1
Step 1: Understand the context of temperature-sensitive mutants in E. coli. These mutants have enzymes or proteins that function normally at a permissive temperature but lose function at a restrictive (higher) temperature, causing observable phenotypic changes such as slow synthesis.
Step 2: Identify what 'synthesis is very slow' refers to. In E. coli, synthesis could mean DNA replication, RNA transcription, or protein translation. Since the problem is general, consider which enzyme or function is critical for the overall synthesis process.
Step 3: Recall that DNA replication requires DNA polymerase, RNA transcription requires RNA polymerase, and protein synthesis requires ribosomes and associated factors. Slow synthesis suggests a bottleneck in one of these key enzymatic activities.
Step 4: Since the problem states 'synthesis is very slow' without specifying which type, the most likely affected enzyme is DNA polymerase if the mutation affects DNA replication, or RNA polymerase if it affects transcription. Consider which enzyme's impairment would broadly slow down synthesis.
Step 5: Conclude that the mutation likely affects an enzyme essential for nucleic acid synthesis, such as DNA polymerase or RNA polymerase, causing the observed slow synthesis phenotype at the restrictive temperature.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Temperature-Sensitive Mutations
Temperature-sensitive mutations cause proteins to function normally at a permissive temperature but lose activity at a restrictive, usually higher, temperature. This allows researchers to study essential genes by observing phenotypic changes when the temperature shifts, revealing the role of the mutated enzyme or function.
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Mutations and Phenotypes
Enzymes Involved in DNA Replication and Synthesis
DNA synthesis in E. coli requires enzymes like DNA polymerase, helicase, primase, and ligase. Mutations affecting these enzymes can slow or halt DNA replication, leading to slow synthesis. Identifying which enzyme is impaired helps explain the observed phenotype.
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Phenotypic Effects of Mutations on Cellular Processes
Mutations in genes encoding enzymes involved in critical processes like DNA replication manifest as observable phenotypes, such as slow synthesis. Understanding how mutations alter enzyme function helps predict which step in the pathway is affected and the resulting cellular consequences.
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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
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.
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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.
Supercoiled strands remain after replication, which is never completed.
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Textbook Question
Many of the gene products involved in DNA synthesis were initially defined by studying mutant E. coli strains that could not synthesize DNA.
The dnaE gene encodes the α subunit of DNA polymerase III. What effect is expected from a mutation in this gene? How could the mutant strain be maintained?
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Textbook Question
Many of the gene products involved in DNA synthesis were initially defined by studying mutant E. coli strains that could not synthesize DNA.
The dnaQ gene encodes the ε subunit of DNA polymerase. What effect is expected from a mutation in this gene?
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