Textbook Question
DNA polymerase III is the main DNA-synthesizing enzyme in bacteria. Describe how it carries out its role of elongating a strand of DNA.
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 12
Explain how RNA participates in DNA replication.
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RNA plays a role in DNA replication by providing a starting point for DNA synthesis. This is achieved through the synthesis of short RNA primers by the enzyme primase.
Primase synthesizes RNA primers complementary to the DNA template strand. These primers are typically 10-12 nucleotides long and are necessary because DNA polymerase cannot initiate synthesis on its own; it requires a free 3' hydroxyl group to add nucleotides.
Once the RNA primer is in place, DNA polymerase begins synthesizing the new DNA strand by adding deoxyribonucleotides to the 3' end of the primer, extending the strand in the 5' to 3' direction.
As replication progresses, the RNA primers are eventually removed by enzymes such as RNase H or DNA polymerase I, which degrade the RNA and replace it with DNA nucleotides.
Finally, DNA ligase seals the gaps between the newly synthesized DNA fragments (Okazaki fragments on the lagging strand), ensuring the continuity of the DNA molecule.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Role of RNA Primase
RNA primase is an enzyme that synthesizes short RNA primers during DNA replication. These primers provide a starting point for DNA polymerase, which cannot initiate synthesis without a primer. The RNA primers are complementary to the DNA template and are later replaced by DNA nucleotides.
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Transcription vs. Replication
While DNA replication involves copying the entire DNA molecule, transcription is the process of synthesizing RNA from a DNA template. Understanding this distinction is crucial, as RNA's role in replication is primarily as a primer, whereas in transcription, RNA serves as a messenger carrying genetic information from DNA to ribosomes for protein synthesis.
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Semiconservative Replication
Okazaki Fragments
During DNA replication, the lagging strand is synthesized discontinuously in short segments known as Okazaki fragments. Each fragment begins with an RNA primer laid down by RNA primase. These fragments are later joined together by DNA ligase, highlighting the essential role of RNA in facilitating the replication of the lagging strand.
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Related Practice
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.
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
A sample of double-stranded DNA is found to contain 20% cytosine. Determine the percentage of the three other DNA nucleotides in the sample.
Textbook Question
Bacterial DNA polymerase I and DNA polymerase III perform different functions during DNA replication.
Identify the principal functions of each molecule.
Textbook Question
Bacterial DNA polymerase I and DNA polymerase III perform different functions during DNA replication.
If mutation inactivated DNA polymerase I in a strain of E. coli, would the cell be able to replicate its DNA? If so, what kind of abnormalities would you expect to find in the cell?
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