Types of DNA Repair Mechanisms
The four primary types of DNA repair are crucial for preventing the different DNA damage that can occur due to environmental factors like ultraviolet radiation, toxic chemicals, and even natural cellular processes that produce various forms of damage to our DNA. This damage, if left unchecked, can lead to mutations, disrupted functions, or even cancer. DNA Repair mechanisms are thus vital in preserving genomic stability.
- Base Excision Repair (BER): It repairs the small and non-helix-distorting lesions. DNA glycosylases recognize and remove damaged bases, creating a basic site. Other enzymes then cut the DNA backbone, remove the damaged section, and fill in the gap with the correct bases.
- Nucleotide Excision Repair (NER): It repairs large and distorting lesions like thymine dimers. NER involves damage recognition, unwinding of the DNA helix, removal of a short single-stranded DNA segment and synthesis of a replacement strand.
- Mismatch Repair (MMR): MMR repairs errors that escape scan during replication of DNA, such as base-base conflict and insertion-deletion. MMR increases the stability of DNA replication, preventing microsatellite instability, a symbol of certain types of cancer.
- Homologous Recombination and Non-Homologous End Joining (NHEJ): These repair double-strand breaks, the most toxic form of DNA damage. HR, an error-free process, uses a homologous DNA sequence for repair, and NHEJ, more error-prone, directly joins the broken DNA ends.
Some forms of DNA damage are directly reversible. For example, the enzyme photolyase can directly reverse UV-induced thymine dimers, a common type of DNA damage, but this mechanism is mostly found in bacteria and some plants and animals and not in humans.
DNA Repair – Damage & Types of Repair
DNA Repair is an important process in which cells recognize and rectify damage to the DNA molecules that make up their genetic material. DNA Repair is an important process as it protects cells from environmental damage and in the ageing process. In human beings, metabolic activities and environment-related factors such as UV rays contribute to DNA damage, resulting in 1 million lesions per cell every day these can damage the structure of the DNA molecule and if they are not repaired, then damage can cause mutations, cellular dysfunction, cancer, and ageing. The preservation of genetic integrity is most important for the survival of an organism and the efficiency of repair mechanisms is crucial for the maintenance of the stability.
Table of Content
- What is DNA Repair?
- DNA Repair and Damage
- DNA Damage
- Sources of DNA Damage
- Types of DNA Repair Mechanisms
- Significance of DNA repair
- Conclusion