This lecture covers the mechanisms by which cells repair DNA damage, including direct repair, base excision repair, nucleotide excision repair, mismatch repair, and non-homologous end joining. The instructor explains how enzymes like photolyase repair UV-induced DNA damage, and how different repair systems target specific types of lesions. The lecture also delves into the detailed steps involved in base excision repair and nucleotide excision repair, highlighting the importance of these processes in maintaining genomic integrity.