Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Chapter 1 Life Forms and Their Origins
- Chapter 2 Nucleic Acids
- Chapter 3 Proteins
- Chapter 4 Simple Chromosomes
- Chapter 5 Chromosomes of Eukarya
- Chapter 6 Genome Content
- Chapter 7 RNA Synthesis 1: Transcription
- Chapter 8 RNA Synthesis 2: Processing
- Chapter 9 Abundance of RNAs in Bacteria
- Chapter 10 Abundance of RNAs in Eukarya
- Chapter 11 Protein Synthesis
- Chapter 12 DNA Replication
- Chapter 13 Chromosome Replication
- Chapter 14 Molecular Events of Recombination
- Chapter 15 Micromutations
- Chapter 16 Repair of Altered DNA
- Chapter 17 Reproduction of Bacteria
- Chapter 18 Horizontal Gene Transfer in Bacteria
- Chapter 19 Cell Cycles of Eukarya
- Chapter 20 Meiosis
- Chapter 21 Chromosomal Abnormalities
- Chapter 22 Life Cycles of Eukarya
- Chapter 23 Reproduction of Viruses
- Chapter 24 Genetic Processes in Development
- Chapter 25 Sex Determination and Dosage Compensation
- Chapter 26 Cancer
- Chapter 27 Cutting, Sorting, and Copying DNA
- Chapter 28 Genotyping by DNA Analysis
- Chapter 29 Genetically Engineered Organisms
- Chapter 30 Genomics
- Chapter 31 Behavior of Genes and Alleles
- Chapter 32 Probability and Statistics Toolkit
- Chapter 33 Genes, Environment, and Interactions
- Chapter 34 Locating Genes
- Chapter 35 Finding and Detecting Mutations
- Chapter 36 Cytoplasmic Inheritance
- Chapter 37 Genetic Variation in Populations
- Chapter 38 Mutation, Migration, and Genetic Drift
- Chapter 39 Natural Selection
- Chapter 40 Quantitative Genetics
- Chapter 41 Speciation
- Chapter 42 Molecular Evolution and Phylogeny
- Glossary
- Index
Chapter 13 - Chromosome Replication
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Chapter 1 Life Forms and Their Origins
- Chapter 2 Nucleic Acids
- Chapter 3 Proteins
- Chapter 4 Simple Chromosomes
- Chapter 5 Chromosomes of Eukarya
- Chapter 6 Genome Content
- Chapter 7 RNA Synthesis 1: Transcription
- Chapter 8 RNA Synthesis 2: Processing
- Chapter 9 Abundance of RNAs in Bacteria
- Chapter 10 Abundance of RNAs in Eukarya
- Chapter 11 Protein Synthesis
- Chapter 12 DNA Replication
- Chapter 13 Chromosome Replication
- Chapter 14 Molecular Events of Recombination
- Chapter 15 Micromutations
- Chapter 16 Repair of Altered DNA
- Chapter 17 Reproduction of Bacteria
- Chapter 18 Horizontal Gene Transfer in Bacteria
- Chapter 19 Cell Cycles of Eukarya
- Chapter 20 Meiosis
- Chapter 21 Chromosomal Abnormalities
- Chapter 22 Life Cycles of Eukarya
- Chapter 23 Reproduction of Viruses
- Chapter 24 Genetic Processes in Development
- Chapter 25 Sex Determination and Dosage Compensation
- Chapter 26 Cancer
- Chapter 27 Cutting, Sorting, and Copying DNA
- Chapter 28 Genotyping by DNA Analysis
- Chapter 29 Genetically Engineered Organisms
- Chapter 30 Genomics
- Chapter 31 Behavior of Genes and Alleles
- Chapter 32 Probability and Statistics Toolkit
- Chapter 33 Genes, Environment, and Interactions
- Chapter 34 Locating Genes
- Chapter 35 Finding and Detecting Mutations
- Chapter 36 Cytoplasmic Inheritance
- Chapter 37 Genetic Variation in Populations
- Chapter 38 Mutation, Migration, and Genetic Drift
- Chapter 39 Natural Selection
- Chapter 40 Quantitative Genetics
- Chapter 41 Speciation
- Chapter 42 Molecular Evolution and Phylogeny
- Glossary
- Index
Summary
Overview
The mode of chromosome replication varies from life form to life form and fits with chromosome structure and with the course and tempo of reproduction.
Chromosome replication begins at origins of replication and stops at termination sequences; small chromosomes typically have a single origin. Replication may be bidirectional or unidirectional. Linear chromosomes may have interior or terminal origins. Most linear chromosomes have telomeres, which are terminal sequences that are replicated in special ways. The large, linear chromosomes of eukarya are divided into many replicons (simultaneously replicated regions), each having an origin at its center.
Chromosomes made of RNA or single-stranded DNA replicate by exceptional mechanisms.
Replication of Circular Chromosomes
Theta Replication
Many circular chromosomes – bacterial chromosomes, most plasmids, and some dsDNA viral chromosomes – replicate by the theta mechanism, so named because the shape of partly replicated chromosomes resembles the Greek letter theta. Theta replication is usually bidirectional, but in some chromosomes it is unidirectional – e.g., colE1 phage.
Replication begins at the chromosome's origin (Figure 13.1). In Escherichia coli the origin is called oriC, which consists of 245 bp and contains short repeated sequences: four copies of a 9-bp sequence and three copies of a 13-bp sequence. First, about 30 copies of initiator protein (dnaA) bind to the four 9-bp sequences of oriC. DnaA helps the DNA to melt, making a single-stranded region. Helicase + dnac bind to the three 13-bp sequences and open up the double-stranded DNA (dsDNA) further, after which two primosomes are assembled and bidirectional replication starts (Figure 13.2).
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- Fundamental Genetics , pp. 115 - 123Publisher: Cambridge University PressPrint publication year: 2004