(1) The document discusses various mechanisms that cells use to repair damage to DNA, including damage from environmental factors, metabolic byproducts, and replication errors. (2) It describes several pathways of repair such as nucleotide excision repair, base excision repair, mismatch repair, photoreactivation, and others. (3) Nucleotide excision repair involves recognizing and removing bulky lesions from DNA and replacing the excised section using the complementary strand as a template for repair synthesis.