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. 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 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
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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
Predict the results of the experiment by Taylor, Woods, and Hughes if replication were
(a) conservative and
(b) dispersive.
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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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