Textbook Question
Outline the current model for DNA synthesis.
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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 15
List the proteins that unwind DNA during in vivo DNA synthesis. How do they function?
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Identify the key proteins involved in unwinding DNA during in vivo DNA synthesis. These typically include helicase, single-strand binding proteins (SSBs), and topoisomerase.
Explain the role of helicase: it binds to the DNA at the origin of replication and moves along the DNA, breaking the hydrogen bonds between complementary base pairs to separate the two strands, creating the replication fork.
Describe the function of single-strand binding proteins (SSBs): after helicase unwinds the DNA, SSBs bind to the exposed single-stranded DNA to prevent the strands from re-annealing or forming secondary structures.
Discuss the role of topoisomerase: as helicase unwinds the DNA, it creates supercoiling tension ahead of the replication fork. Topoisomerase alleviates this tension by making temporary cuts in the DNA backbone, allowing it to unwind and then resealing the cuts.
Summarize how these proteins work together to ensure the DNA strands are properly separated and stabilized, allowing DNA polymerase to synthesize new strands efficiently.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Helicase
Helicase is an enzyme that unwinds the DNA double helix by breaking the hydrogen bonds between complementary base pairs. This action separates the two strands, creating replication forks and allowing the DNA polymerase to access single-stranded DNA for synthesis.
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11:59
Steps to DNA Replication
Single-Strand Binding Proteins (SSBs)
Single-strand binding proteins bind to the separated DNA strands after helicase unwinds them, stabilizing the single-stranded DNA and preventing it from re-annealing or forming secondary structures. This ensures the strands remain accessible for replication.
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03:51Recombination after Single Strand Breaks
Topoisomerase
Topoisomerase relieves the torsional strain generated ahead of the replication fork by making transient cuts in the DNA backbone. This prevents supercoiling and tangling, facilitating smooth unwinding and progression of the replication machinery.
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03:07Supercoiling
Related Practice
Textbook Question
List and describe the function of the ten subunits constituting DNA polymerase III. Distinguish between the holoenzyme and the core enzyme.
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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
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
Distinguish between
(a) unidirectional and bidirectional synthesis, and
(b) continuous and discontinuous synthesis of DNA.
Textbook Question
Summarize and compare the properties of DNA polymerase I, II, and III.
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