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Glossary Term
Drug-, radiation-induced, or spontaneous injuries to DNA that introduce deviations from its normal double-helical conformation. These changes include structural distortions that interfere with replication and transcription, as well as point mutations that disrupt base pairs and exert damaging effects on future generations through changes in DNA sequence. If the damage is minor, it can often be repaired (DNA repair); extensive damage can induce apoptosis.
Glossary Term
The mismatch repair (MMR) system promotes genomic fidelity by repairing base-base mismatches, insertion-deletion loops and heterologies generated during DNA replication and recombination. This function is critically dependent on the assembly of multimeric complexes involved in mismatch recognition and signal transduction to downstream repair events.
Glossary Term
Any transmissible change in the genetic material of an organism, which can result from radiation, viral infection, transposition, treatment with mutagenic chemicals and errors during DNA replication or meiosis. The effects of mutation range from single base changes to loss or gain of complete chromosomes. As many of the simpler alterations to DNA may be repaired, such changes are only heritable once the change is fixed in the DNA by the process of replication. Mutations may be associated with genetic diversity or with pathologies including cancer.
Glossary Term
Nucleotide Excision Repair (NER) mends DNA regions that contain chemical adducts, such as UV-induced thymine dimers or carcinogenic adducts, which distort the DNA helix and interfere with replication and transcription. NER is targeted to actively transcribed regions of the genome. During NER in eukaryotes, shape irregularities are detected by protein complexes that slide along the DNA molecule and induce cuts on each side of a lesion several nucleotides away. Removal of the damaged 25-30 nucleotide fragment is followed by repair synthesis and ligation.
Glossary Term
A small-scale mutation in which a single nucleotide is exchanged for another. Mutagenic chemicals and mistakes in DNA replication may result in point mutations.
Glossary Term
An RNA-dependent DNA polymerase that is involved in the replication of retroviruses an in the maintenance of telomeres.
Glossary Term
A stretch of repetitive nucleotide sequences (TTAGGG repeats in humans) found at both ends of each chromatid arm that plays a role in chromosome stability during replication.
