This lecture covers the mechanisms of DNA repair, focusing on base excision repair (BER), nucleotide excision repair (NER), non-homologous end joining (NHEJ), and homologous recombination (HR). BER and NER require an intact second strand as a template for repair, while NHEJ is used when there is no sister chromatid available. HR is a high-fidelity process that uses a sister chromatid as a repair template. The lecture also discusses the consequences of mutations in DNA repair enzymes and inherited syndromes related to DNA repair defects, such as xeroderma pigmentosum and ataxia telangiectasia.