This article discusses the mechanisms of DNA damage, repair, and mutagenesis, highlighting the importance of these processes in maintaining genomic stability and preventing diseases such as cancer. The article outlines the various types of DNA damage, including endogenous and exogenous sources, and the repair pathways that cells use to correct these damages. Key repair mechanisms include base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR), and non-homologous end joining (NHEJ). Additionally, the article covers the role of translesion synthesis (TLS) polymerases in bypassing DNA damage during replication. The importance of these mechanisms is emphasized in the context of cancer, aging, and neurodegenerative disorders. The article also discusses the impact of environmental factors, such as ionizing radiation, ultraviolet radiation, and chemical agents, on DNA damage and the repair processes that counteract these effects. The review concludes with an overview of the DNA damage response (DDR) and the various repair pathways that ensure genomic stability.This article discusses the mechanisms of DNA damage, repair, and mutagenesis, highlighting the importance of these processes in maintaining genomic stability and preventing diseases such as cancer. The article outlines the various types of DNA damage, including endogenous and exogenous sources, and the repair pathways that cells use to correct these damages. Key repair mechanisms include base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR), and non-homologous end joining (NHEJ). Additionally, the article covers the role of translesion synthesis (TLS) polymerases in bypassing DNA damage during replication. The importance of these mechanisms is emphasized in the context of cancer, aging, and neurodegenerative disorders. The article also discusses the impact of environmental factors, such as ionizing radiation, ultraviolet radiation, and chemical agents, on DNA damage and the repair processes that counteract these effects. The review concludes with an overview of the DNA damage response (DDR) and the various repair pathways that ensure genomic stability.