Textbook Question
Kornberg showed that nucleotides are added to the 3' end of each growing DNA strand. In what way does an exposed 3'-OH group participate in strand elongation?
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Ch. 11 - DNA Replication and Recombination
Klug12th EditionConcepts of Genetics ISBN: 9780135564776
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Table of contents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Chapter 11, Problem 9
Which characteristics of DNA polymerase I raised doubts that its in vivo function is the synthesis of DNA leading to complete replication?
Verified step by step guidance1
Understand the primary known activities of DNA polymerase I, which include its 5' to 3' polymerase activity, 3' to 5' exonuclease proofreading activity, and 5' to 3' exonuclease activity.
Recognize that DNA polymerase I has relatively low processivity, meaning it can add only a limited number of nucleotides before dissociating from the DNA template.
Note that DNA polymerase I's 5' to 3' exonuclease activity allows it to remove RNA primers but also limits its ability to synthesize long stretches of DNA continuously.
Consider that the enzyme's slower rate of DNA synthesis compared to other polymerases suggests it is not the main enzyme responsible for rapid and complete DNA replication.
Conclude that these characteristics—low processivity, presence of 5' to 3' exonuclease activity, and slower synthesis rate—raised doubts about DNA polymerase I being the primary enzyme for complete DNA replication in vivo.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Polymerase I Enzymatic Activities
DNA Polymerase I possesses multiple enzymatic functions, including 5' to 3' polymerase activity, 3' to 5' exonuclease proofreading, and 5' to 3' exonuclease activity. The presence of the 5' to 3' exonuclease allows it to remove RNA primers, but its relatively slow polymerization rate compared to other polymerases raised questions about its role in complete DNA replication.
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05:44
Repair Pathways
Processivity of DNA Polymerase I
Processivity refers to the number of nucleotides a polymerase can add before dissociating from the DNA template. DNA Polymerase I has low processivity, meaning it frequently dissociates, which is inefficient for synthesizing long DNA strands required for complete replication, suggesting it may not be the main enzyme for this task.
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Role of DNA Polymerase I in DNA Replication vs. Repair
While DNA Polymerase I can synthesize DNA, its primary in vivo role is believed to be removing RNA primers and filling short gaps during DNA repair and Okazaki fragment processing. This specialized function contrasts with the high-speed, high-processivity synthesis needed for complete genome replication, implicating other polymerases in that role.
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Related Practice
Textbook Question
How did Kornberg assess the fidelity of DNA polymerase I in copying a DNA template?
Textbook Question
What are the requirements for in vitro synthesis of DNA under the direction of DNA polymerase I?
Textbook Question
In Kornberg's initial experiments, it was rumored that he grew E. coli in Anheuser-Busch beer vats. (Kornberg was working at Washington University in St. Louis.) Why do you think this might have been helpful to the experiment?
Textbook Question
What was the significance of the polA1 mutation?
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Textbook Question
Summarize and compare the properties of DNA polymerase I, II, and III.
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