DNA repair is a cellular mechanism that aims to maintain the integrity and stability of the DNA molecule. DNA can be damaged by various factors, including environmental agents (such as radiation and chemicals) and internal cellular processes (such as errors during DNA replication). Unrepaired or misrepaired DNA damage can lead to mutations and genomic instability, which can have detrimental effects on cellular function and contribute to the development of diseases, including cancer.
DNA repair mechanisms operate at the molecular level and involve complex processes that detect, remove, and repair damaged DNA. There are several major DNA repair pathways, including:
Base Excision Repair (BER): BER repairs DNA damage involving individual damaged bases, such as those caused by oxidation or chemical modifications. It involves the removal of the damaged base by specific enzymes and subsequent replacement with the correct base.
Nucleotide Excision Repair (NER): NER repairs a wide range of DNA lesions, including those caused by UV radiation or certain chemicals. It involves the removal of a segment of damaged DNA containing the lesion and subsequent synthesis of a new DNA strand using the undamaged complementary strand as a template.
Mismatch Repair (MMR): MMR corrects errors that occur during DNA replication, such as the misincorporation of incorrect nucleotides. It recognizes and removes the mismatched base pairs and replaces them with the correct ones.
Homologous Recombination (HR): HR repairs double-strand breaks (DSBs) in DNA, which can occur due to exposure to radiation or other damaging agents. It utilizes a template from a sister chromatid or homologous chromosome to restore the missing or damaged DNA sequence.
Non-Homologous End Joining (NHEJ): NHEJ repairs DSBs in DNA without the need for a homologous template. It directly joins the broken DNA ends, often resulting in small insertions or deletions at the repair site.
These are just a few examples of the many DNA repair mechanisms that exist in cells. The specific repair pathway utilized depends on the type and extent of DNA damage. These repair processes play a crucial role in maintaining genome integrity, preserving genetic information, and ensuring proper cellular function.