Base excision repair primarily addresses what kind of DNA alterations?

Base excision repair is a critical mechanism in the cellular machinery that specifically recognizes and repairs small, non-helix-deforming lesions in DNA. These lesions often arise from the spontaneous hydrolysis of bases, oxidative stress, or exposure to certain chemicals, resulting in modifications such as deamination, oxidation, or alkylation of individual bases.

The primary process of base excision repair involves the removal of the damaged base by a specific DNA glycosylase, followed by the cleavage of the sugar-phosphate backbone by an AP endonuclease. This is then followed by the repair of the site through DNA polymerase, which fills in the gap, and DNA ligase, which seals the newly synthesized piece into the DNA strand.

In contrast, large structural changes to DNA would involve different repair mechanisms, such as nucleotide excision repair or homologous recombination, which are more suited for extensive damage, while complete breaks in DNA strands, known as double-strand breaks, are repaired by specialized pathways like non-homologous end joining or homologous recombination. Mismatch errors during replication are specifically corrected by the mismatch repair system, which identifies and repairs incorrectly paired bases. Thus, base excision repair is uniquely designed to efficiently handle small