DNA repair is a crucial process that ensures the integrity of genetic information within cells. Even minor mutations in DNA can lead to significant consequences for cellular function and health. Fortunately, cells possess a variety of DNA repair mechanisms that are conserved across all life forms. Understanding these mechanisms is essential for grasping how cells maintain their genetic stability.
The DNA repair mechanisms can be categorized into four main groups:
- Repair of nucleotide mismatches
- Repair of damaged DNA
- Repair of thymine dimers
- Repair of extensive mutations and damage
Initially, we will focus on the mechanisms that address nucleotide mismatches, which include:
- DNA Polymerase proofreading: This process involves the enzyme DNA polymerase, which checks and corrects errors during DNA replication, ensuring that the correct nucleotides are incorporated.
- Mismatch repair: This mechanism identifies and repairs mismatched base pairs that escape the proofreading activity of DNA polymerase.
Following the discussion on nucleotide mismatches, we will explore the repair of damaged DNA, specifically through:
- Base excision repair: This process removes and replaces damaged or non-canonical bases in the DNA.
Next, we will examine the repair of thymine dimers, which are often caused by UV radiation. This includes:
- Nucleotide excision repair: This mechanism removes a short single-strand segment of DNA containing the dimer and fills in the gap with the correct nucleotides.
- Photo reactivation: This is a light-dependent repair mechanism that directly reverses thymine dimers.
Finally, we will discuss the SOS repair system, which is activated in response to extensive DNA damage, allowing cells to bypass lesions that would otherwise stall replication.
As we progress through these topics, we will delve deeper into each DNA repair mechanism, starting with DNA polymerase proofreading in the next section.
