What type of DNA damage does nucleotide excision repair primarily fix?

Nucleotide excision repair (NER) is a critical DNA repair mechanism that primarily targets specific types of DNA damage, particularly thymine dimers and bulky adducts. Thymine dimers occur when two adjacent thymine bases bond together due to UV radiation, resulting in a distortion in the DNA structure that can impede replication and transcription. Bulky adducts, on the other hand, can arise from exposure to certain chemicals or environmental factors, leading to significant disruptions in the DNA structure.

The NER process involves recognizing the distortion caused by these types of damage, excising the damaged segment of DNA, and then synthesizing a new strand to restore the original sequence. This mechanism is vital for maintaining genomic integrity, as failure to repair such damage can lead to mutations and contribute to various diseases, including cancer.

In contrast, single-strand breaks are typically repaired by other mechanisms like base excision repair or homologous recombination. DNA cross-linking involves connecting two DNA strands together in an abnormal manner, which is addressed by a different repair pathway known as the cross-link repair pathway. Base pair mismatches are primarily corrected through mismatch repair mechanisms that specifically target errors that occur during DNA replication. Thus, while these other forms of damage are significant,