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.
In Base Excision Repair an Altered Base Is Removed by a DNA Glycosylase Enzyme Followed by Excision of the Resulting Sugar Phosphate. the Small Gap Left in the DNA Helix Is Filled in by the Sequential Action of DNA Polymerase and DNA Ligase.
A DNA Repair Process in Which a Small Region of the Strand Surrounding the Damage Is Removed From the DNA Helix As an Oligonucleotide. the Small Gap Left in the DNA Helix Is Filled in by the Sequential Action of DNA Polymerase and DNA Ligase. Nucleotide Excision Repair Recognizes a Wide Range of Substrates Including Damage Caused by Uv Irradiation (pyrimidine Dimers and 6 4 Photoproducts) and Chemicals (intrastrand Cross Links and Bulky Adducts).
DNA-(apurinic or apyrimidinic site) lyase activity
Catalysis of the Cleavage of the C O P Bond 3' to the Apurinic or Apyrimidinic Site in DNA by a Beta Elimination Reaction Leaving a 3' Terminal Unsaturated Sugar and a Product with a Terminal 5' Phosphate.