Base excision repair

Definition

Base excision repair is a cellular mechanism that corrects DNA damage caused by the spontaneous deamination of bases, oxidation, or the incorporation of incorrect bases. This repair process is crucial for maintaining genomic stability by removing and replacing damaged or mispaired bases before they can lead to mutations during DNA replication.

5 Must Know Facts For Your Next Test

1. Base excision repair primarily targets non-helix-distorting base lesions, which are often caused by oxidative stress or alkylation.
2. The process begins when DNA glycosylases detect and remove the damaged base, leaving behind an AP site.
3. AP endonuclease then cleaves the DNA backbone at the AP site, creating a nick for further repair.
4. Following the cleavage, DNA polymerase fills in the gap with the correct nucleotide before DNA ligase seals the final nick in the backbone.
5. Base excision repair is essential for preventing mutations that can lead to cancer and other genetic disorders, highlighting its importance in cellular health.

Review Questions

• How does base excision repair initiate, and what is the role of DNA glycosylase in this process?
  • Base excision repair starts when DNA glycosylase recognizes a damaged or incorrect base within the DNA. This enzyme removes the problematic base, creating an AP site that signals for further action. The removal of the base is critical as it prevents replication errors from occurring, ensuring genomic integrity.
• What are the key steps following the creation of an AP site during base excision repair?
  • After an AP site is formed by the removal of a damaged base, an enzyme called AP endonuclease cleaves the DNA backbone at that site. This creates a nick in the strand, which is then filled in by DNA polymerase adding the correct nucleotide. Finally, DNA ligase seals the nick to restore the integrity of the DNA strand.
• Evaluate the significance of base excision repair in relation to genetic stability and disease prevention.
  • Base excision repair plays a critical role in maintaining genetic stability by correcting minor but potentially harmful DNA damages that can occur due to environmental factors or normal cellular processes. When this mechanism operates correctly, it helps prevent mutations that could lead to diseases such as cancer. Any defects or inefficiencies in this repair pathway can increase susceptibility to genetic disorders and compromise cellular health, emphasizing its importance in disease prevention.

Related terms

DNA glycosylase: An enzyme that recognizes and removes damaged or inappropriate bases from DNA, initiating the base excision repair process.

AP site: A site in DNA that has lost a purine or pyrimidine base, created during base excision repair when the damaged base is removed.

DNA polymerase: An enzyme responsible for synthesizing new DNA strands by adding nucleotides during DNA replication and repair processes, including base excision repair.