which of the dna activities play a role in repairing dna defects
The DNA activities that play a role in repairing DNA defects are
1. Mismatch repair System: This system corrects errors that occurred during DNA replication, for example, when the wrong base is added to a new strand.
2. Nucleotide Excision Repair: This system corrects damage that results from UV radiation and other chemical damage, such as chemicals in cigarette smoke that can cause mutations.
3. Base Excision Repair: This system corrects damage caused by free radicals—chemically unstable molecules that can damage DNA and other molecules in the body.
4. Homologous Recombination: This system repairs double-strand breaks in DNA that occur during replication or in response to DNA damage.
5. Non-homologous end joining (NHEJ): This system repairs double-strand breaks in DNA by rejoining the broken ends.
There are several major DNA repair activities that help in repairing DNA defects. These include:
1. Mismatch repair (MMR): MMR corrects errors that occur during DNA replication and recombination, where the newly synthesized DNA strand does not perfectly match the template strand.
2. Nucleotide excision repair (NER): NER repairs bulky DNA lesions caused by exposure to ultraviolet (UV) light and certain chemicals. It removes and replaces a small region of damaged DNA, including thymine dimers and chemically modified bases.
3. Base excision repair (BER): BER is involved in repairing damaged DNA bases, such as those caused by oxidative stress or exposure to certain chemicals. It removes the damaged base and replaces it with the correct one.
4. Homologous recombination (HR): HR repairs double-strand breaks in DNA, which might occur due to exposure to ionizing radiation or from errors during DNA replication. This repair process uses the homologous DNA sequence as a template to fill in the missing information.
5. Non-homologous end joining (NHEJ): NHEJ is another pathway for repairing double-strand breaks in DNA. In this process, the broken ends of DNA are directly ligated together without the need for a homologous template.
These various DNA repair activities work collaboratively in maintaining the integrity of the DNA molecule and ensuring proper functioning of the cells.