How is damaged DNA repaired?
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.
How do DNA repair mechanisms detect and repair damaged DNA?
The enzymes remove the damaged base forming an AP site which is repaired by AP endonuclease before the nucleotide gap in the DNA strand is filled by DNA polymerase. In mismatch repair, the missed errors are later corrected by enzymes which recognize and excise the mismatched base to restore the original sequence.
What are the 3 repair processes that help fix damaged DNA?
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).
Which damage is the simplest DNA repair system?
The simplest and most accurate repair mechanism is the direct reversal of damage in a single-step reaction. Direct reversal, however, applies to only a very limited number of DNA lesions.
How are DNA mutations repaired?
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.
Which DNA repair pathway can recognize DNA damage during transcription?
Nucleotide excision repair
Nucleotide excision repair (NER) is the main repair pathway that removes DNA helix-distorting lesions, either in the transcribed strand, by its sub-pathway transcription-coupled nucleotide excision repair (TC-NER), or genome-wide, by the sub-pathway global genome nucleotide excision repair (GG-NER; Supplementary Box 1) …
How does DNA get damaged?
DNA can be damaged via environmental factors as well. Environmental agents such as UV light, ionizing radiation, and genotoxic chemicals. Replication forks can be stalled due to damaged DNA and double strand breaks are also a form of DNA damage.
What happens when DNA is damaged?
DNA damage can affect normal cell replicative function and impact rates of apoptosis (programmed cell death, often referred to as ‘cellular senescence’). Alternatively, damage to genetic material can result in impaired cellular function, cell loss, or the transformation of healthy cells to cancers.