Final answer:
Nucleotide excision repair is designed to fix larger regions of damaged DNA, specifically involving an excision nuclease that makes cuts surrounding the damage before the area is repaired and resealed by DNA polymerase and DNA ligase.
Step-by-step explanation:
Nucleotide excision repair differs from base excision repair primarily because it is designed to repair larger regions of DNA damage. This mechanism involves the recognition of bulky, helix-distorting DNA damage such as thymine dimers, rather than just single base changes. After identifying the damage, an excision nuclease makes cuts on both the 3' and 5' ends of the damaged DNA. The damaged strand is removed, and the gap is filled with correctly paired nucleotides with the help of DNA polymerase.
Finally, DNA ligase seals the gap with a phosphodiester linkage to complete the repair. In contrast to nucleotide excision repair, base excision repair deals with single nucleotide damage where the damaged base is cut out by a glycosylase enzyme, and the empty site is then filled by new nucleotides and sealed by DNA ligase.