Chapter 8
DNA Replication and Repair
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Base-pairing and DNA Repair
Erwin Chargaff’s rules on DNA equivalence paved the way for the discovery of base pairing in DNA. Chargaff’s rules state that in a ...
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The DNA Replication Fork
An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped ...
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Lagging Strand Synthesis
During replication, the complementary strands in double-stranded DNA are synthesized at different rates. Replication first begins on the leading strand. ...
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The Replisome
DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this ...
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Proofreading
Synthesis of new DNA molecules is carried out by the enzyme DNA polymerase, which adds nucleotides on the daughter strand complementary to the template ...
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Replication in Prokaryotes
DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to the ...
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Replication in Eukaryotes
In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high fidelity before ...
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Telomeres and Telomerase
In eukaryotic DNA replication, a single-stranded DNA fragment remains at the end of a chromosome after the removal of the final primer. This section of ...
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Overview of DNA Repair
In order to be passed through generations, genomic DNA must be undamaged and error-free. However, every day, DNA in a cell undergoes several thousand to a ...
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Base Excision Repair
One of the common DNA damages is the chemical alteration of single bases by alkylation, oxidation, or deamination. The altered bases cause mispairing and ...
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Nucleotide Excision Repair
DNA Distortion and Damage
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV ...
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Mismatch Repair
Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the ...
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Fixing Double-strand Breaks
The double-stranded structure of DNA has two major advantages. First, it serves as a safe repository of genetic information where one strand serves as the ...
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Homologous Recombination
The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of ...
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Gene Conversion
Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the ...
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DNA Damage Can Stall the Cell Cycle
In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages ...
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Restarting Stalled Replication Forks
DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the ...
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