Textbook Question
There is a problem completing the replication of linear chromosomes at their ends. Describe the problem and identify why telomeres shorten in each replication cycle.
Ch. 7 - DNA Structure and Replication
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 7, Problem 10
DNA polymerase III is the main DNA-synthesizing enzyme in bacteria. Describe how it carries out its role of elongating a strand of DNA.
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DNA polymerase III begins its role by binding to the primer, which is a short RNA sequence synthesized by primase. This primer provides a free 3'-OH group necessary for DNA polymerase III to initiate DNA synthesis.
The enzyme elongates the DNA strand by adding nucleotides complementary to the template strand. It follows the base-pairing rules: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).
DNA polymerase III synthesizes the new strand in the 5' to 3' direction, meaning it adds nucleotides to the 3'-OH end of the growing strand. This directionality is crucial for proper DNA replication.
The enzyme has high processivity, meaning it can add thousands of nucleotides without dissociating from the DNA template. This is facilitated by the sliding clamp protein, which holds DNA polymerase III tightly to the DNA strand.
DNA polymerase III also has proofreading activity through its 3' to 5' exonuclease function. If an incorrect nucleotide is incorporated, the enzyme can remove it and replace it with the correct one, ensuring high fidelity during DNA replication.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Replication
DNA replication is the biological process by which a cell duplicates its DNA, ensuring that each daughter cell receives an identical copy. This process involves unwinding the double helix and synthesizing new strands complementary to the original templates. DNA polymerase III plays a crucial role in this process by adding nucleotides to the growing DNA strand.
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Steps to DNA Replication
DNA Polymerase III Function
DNA polymerase III is a multi-subunit enzyme responsible for synthesizing new DNA strands during replication. It adds nucleotides in a 5' to 3' direction, using the existing template strand as a guide. This enzyme also has proofreading capabilities, allowing it to correct errors during DNA synthesis, which is vital for maintaining genetic fidelity.
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Leading and Lagging Strands
During DNA replication, the two strands of the double helix are replicated differently. The leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized in short segments called Okazaki fragments, which are later joined together. DNA polymerase III is involved in synthesizing both strands, but its activity differs based on the strand being replicated.
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Related Practice
Textbook Question
Explain how RNA participates in DNA replication.
Textbook Question
Consider the sequence 3'-ACGCTACGTC-5'.
What is the double-stranded sequence?
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Textbook Question
There is a problem completing the replication of linear chromosomes at their ends. What is the function of telomerase, and how does it operate to synthesize telomeres?
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Textbook Question
Consider the sequence 3'-ACGCTACGTC-5'.
What is the total number of noncovalent bonds joining the nucleotides of the complementary strands?
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Textbook Question
Consider the sequence 3'-ACGCTACGTC-5'.
What is the total number of covalent bonds joining the nucleotides in each strand?