Final answer:
Nucleotide excision repair is a DNA repair mechanism that corrects damage by removing the incorrect base and surrounding nucleotides, synthesizing the correct sequence using DNA polymerase, and sealing the section with DNA ligase.
Step-by-step explanation:
Nucleotide Excision Repair Process
Nucleotide excision repair (NER) is a DNA repair mechanism crucial for correcting DNA damage such as thymine dimers, typically caused by UV radiation. This process involves several steps:
- DNA damage recognition by repair enzymes.
- Cutting the damaged DNA strand on both the 3' and 5' ends around the incorrect base.
- Removing the damaged section of DNA, which could affect a longer strand of 2-30 bases.
- Using DNA polymerase to synthesize the correct nucleotides based on the undamaged template strand.
- Sealing the newly synthesized DNA to the original strand with a phosphodiester linkage through the action of DNA ligase.
NER can also specifically target genes that are being actively transcribed through a specialized form known as Transcription-Coupled Repair (TCR).
The importance of this repair mechanism was highlighted by the awarding of the Nobel Prize in Chemistry to Aziz Sancar in 2015 for his work on nucleotide excision repair.