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.
Catalysis of a Biochemical Reaction At Physiological Temperatures. in Biologically Catalyzed Reactions the Reactants Are Known As Substrates and the Catalysts Are Naturally Occurring Macromolecular Substances Known As Enzymes. Enzymes Possess Specific Binding Sites For Substrates and Are Usually Composed Wholly or Largely of Protein But RNA That Has Catalytic Activity (ribozyme) Is Often Also Regarded As Enzymatic.