Mismatch repair

Definition

Mismatch repair is a cellular process that corrects errors that occur during DNA replication, specifically mismatches where bases are paired incorrectly. This system is essential for maintaining genetic stability and preventing mutations, as it ensures that the newly synthesized DNA strands accurately reflect the original template. By addressing these errors, mismatch repair helps mitigate the effects of mutagenesis and contributes to the overall fidelity of DNA replication.

5 Must Know Facts For Your Next Test

1. Mismatch repair is crucial for correcting base-pairing errors that occur during DNA replication, helping to prevent permanent mutations.
2. The mismatch repair system recognizes distortions in the DNA helix caused by mismatched bases and selectively excises the incorrect nucleotides.
3. Key proteins involved in mismatch repair include MutS, which detects mismatches, and MutL, which coordinates the repair process.
4. In eukaryotic cells, mismatch repair also plays a role in maintaining genomic stability by repairing mutations that could lead to cancer.
5. Defects in mismatch repair pathways can lead to conditions like Lynch syndrome, which increases the risk of developing certain types of cancer.

Review Questions

• How does mismatch repair improve the accuracy of DNA replication?
  • Mismatch repair enhances the accuracy of DNA replication by identifying and correcting base-pairing errors that may occur during the synthesis of new DNA strands. The system works by detecting distortions in the DNA structure caused by incorrect base pairs, then excising the erroneous nucleotides before replacing them with the correct ones. This corrective mechanism is vital for maintaining genetic fidelity and reducing the likelihood of mutations being passed on during cell division.
• What roles do key proteins such as MutS and MutL play in the mismatch repair process?
  • MutS and MutL are crucial proteins in the mismatch repair process. MutS detects mismatched bases in the DNA and initiates the repair process by binding to the mismatch site. Once a mismatch is identified, MutL coordinates the recruitment of additional repair enzymes to excise the incorrect nucleotide segments and facilitate their replacement. Together, these proteins ensure that any errors made during DNA replication are efficiently corrected, thus preserving genetic integrity.
• Evaluate the consequences of defective mismatch repair systems on human health and genetic stability.
  • Defective mismatch repair systems can have serious implications for human health, as they significantly increase the risk of accumulating mutations in the genome. One notable consequence is Lynch syndrome, a hereditary condition linked to mutations in mismatch repair genes, which heightens susceptibility to various cancers, particularly colorectal cancer. Additionally, impaired mismatch repair can lead to genomic instability, allowing for unchecked cellular proliferation and tumor formation. This highlights how crucial accurate DNA repair mechanisms are for both individual health and overall genetic stability.

Related terms

DNA polymerase: An enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand during replication.

exonuclease: An enzyme that removes nucleotide residues from the ends of a DNA strand, often used in conjunction with DNA polymerase to correct errors during replication.

mutagenesis: The process by which mutations are generated, which can occur through various mechanisms including errors in DNA replication, chemical exposure, or radiation.