Final answer:
Excision repair, specifically nucleotide excision repair (NER), is a DNA repair process that removes and replaces damaged DNA, such as thymine dimers caused by UV radiation. It involves cutting the damaged DNA, filling the gap with new nucleotides, and sealing the strand, maintaining genetic stability.
Step-by-step explanation:
Excision Repair Mechanisms in DNA
Excision repair is a crucial cellular process used to address DNA damage. Nucleotide excision repair (NER) is a particular type of DNA repair mechanism that involves the removal and replacement of damaged DNA. This process recognizes and excises bulky, helix-distorting nucleotide damage like thymine dimers, which are typically caused by UV radiation. The damaged strand is cut at both the 3' and 5' ends surrounding the lesion, and the damaged segment is excised. DNA polymerase fills in the gap with correct nucleotides, and DNA ligase seals the strand with a phosphodiester linkage, restoring the DNA's integrity. The discovery of the NER process earned Aziz Sancar the Nobel Prize in Chemistry in 2015, highlighting its significance in maintaining genetic stability.