What is DNA damage and repair mechanism?
At least five major DNA repair pathways—base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR) and non-homologous end joining (NHEJ)—are active throughout different stages of the cell cycle, allowing the cells to repair the DNA damage.
What is the most common mechanism for repairing damage to DNA?
Most damage to DNA is repaired by removal of the damaged bases followed by resynthesis of the excised region. Some lesions in DNA, however, can be repaired by direct reversal of the damage, which may be a more efficient way of dealing with specific types of DNA damage that occur frequently.
What are the three major mechanisms of DNA repair?
There are three types of repair mechanisms: direct reversal of the damage, excision repair, and postreplication repair. Direct reversal repair is specific to the damage. For example, in a process called photoreactivation, pyrimidine bases fused by UV light are separated by DNA photolyase (a light-driven enzyme).
What are the two major DNA repair mechanisms?
There are two main mechanisms for repairing double strand breaks: homologous recombination and classical nonhomologous end joining.
What causes DNA damage?
DNA damage occurs continuously as a result of various factors—intracellular metabolism, replication, and exposure to genotoxic agents, such as ionizing radiation and chemotherapy. If left unrepaired, this damage could result in changes or mutations within the cell genomic material.
What is the enzyme that repairs DNA?
DNA ligase, shown above repairing chromosomal damage, is an enzyme that joins broken nucleotides together by catalyzing the formation of an internucleotide ester bond between the phosphate backbone and the deoxyribose nucleotides.
What happens during DNA repair?
Repair processes that help fix damaged DNA include: Direct reversal: Some DNA-damaging chemical reactions can be directly “undone” by enzymes in the cell. Excision repair: Damage to one or a few bases of DNA is often fixed by removal (excision) and replacement of the damaged region.
What is the DNA repair process?
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. Other lesions induce potentially harmful mutations in the cell’s genome, which affect the survival of its daughter cells after it undergoes mitosis.
What is direct repair of DNA?
Direct repair is defined as the elimination of DNA and RNA damage using chemical reversion that does not require a nucleotide template, breakage of the phosphodiester backbone or DNA synthesis.
What happens if DNA is not repaired?
Because DNA is the repository of genetic information in each living cell, its integrity and stability are essential to life. DNA, however, is not inert; rather, it is a chemical entity subject to assault from the environment, and any resulting damage, if not repaired, will lead to mutation and possibly disease.
How do enzymes repair DNA?
Some enzymes work to repair DNA strands. These types of proteins actively travel along a strand to check for any errors or injuries. They repair the strands that are damaged by creating new cells with the correct DNA inscriptions. There are DNA enzymes that attach to certain portions of the strand.
How does DNA repair itself?
DNA does not repair itself, it is repaired by proteins. DNA can undergo several kinds of damage. For each type, there is a mechanism in which specialized proteins recognize the problem, and reconstruct the DNA as good as it goes.
How does UV light damage the DNA strand?
UV light creates damaging links between atoms in the DNA building block thymine. An enzyme called photolyase, which is triggered by a different wavelength of light, cuts them out and repairs the damage.
Can you repair DNA damage?
DNA damages can be recognized by enzymes, and so they can be repaired. Repair needs the undamaged sequence in the complementary DNA strand or in a homologous chromosome. If a cell retains DNA damage, transcription of a gene can be prevented, and, thus, translation into a protein will also be blocked.