The Process of Restoring DNA After Damage. Genomes Are Subject to Damage by Chemical and Physical Agents in the Environment (e.g. Uv and Ionizing Radiations Chemical Mutagens Fungal and Bacterial Toxins Etc.) and by Free Radicals or Alkylating Agents Endogenously Generated in Metabolism. DNA Is Also Damaged Because of Errors During Its Replication. a Variety of Different DNA Repair Pathways Have Been Reported That Include Direct Reversal Base Excision Repair Nucleotide Excision Repair Photoreactivation Bypass Double Strand Break Repair Pathway and Mismatch Repair Pathway.
Any Process That Results in a Change in State or Activity of a Cell (in Terms of Movement Secretion Enzyme Production Gene Expression Etc.) As a Result of a Stimulus Indicating Damage to Its DNA From Environmental Insults or Errors During Metabolism.