Mismatch repair

Definition

Mismatch repair is a cellular mechanism that corrects errors that occur during DNA replication, ensuring the fidelity of genetic information. This process is crucial in maintaining genetic stability by identifying and repairing incorrectly paired nucleotides, which can arise from replication mistakes or external factors. By fixing these mismatches, cells prevent the accumulation of mutations that can lead to diseases such as cancer.

5 Must Know Facts For Your Next Test

1. Mismatch repair primarily occurs shortly after DNA replication when newly synthesized strands are still associated with the original template strands.
2. The process involves several key proteins, including MutS, MutL, and MutH, which work together to identify and excise mismatched bases.
3. Defects in mismatch repair can lead to microsatellite instability, a hallmark of certain types of cancer, such as Lynch syndrome.
4. In addition to correcting replication errors, mismatch repair plays a role in enhancing the overall mutation rate of organisms by influencing how mutations are fixed or removed.
5. This repair mechanism is conserved across many organisms, highlighting its importance in maintaining genomic integrity throughout evolution.

Review Questions

• How does mismatch repair enhance the fidelity of DNA replication?
  • Mismatch repair enhances the fidelity of DNA replication by correcting base-pairing errors that occur during the synthesis of new DNA strands. After DNA polymerase incorporates nucleotides, mismatch repair proteins identify mispaired bases and remove them. This ensures that the correct nucleotides are inserted, thus preventing mutations from being passed on during cell division.
• Discuss the consequences of defects in the mismatch repair system on genetic stability.
  • Defects in the mismatch repair system can severely compromise genetic stability by allowing replication errors to persist. When mismatches are not corrected, they can lead to an accumulation of mutations over generations. This can result in conditions like Lynch syndrome, where individuals have an increased risk for various cancers due to unresolved DNA errors that propagate through cell divisions.
• Evaluate the role of mismatch repair in evolutionary processes and its implications for understanding cancer biology.
  • Mismatch repair plays a critical role in evolutionary processes by maintaining genetic stability and preventing the fixation of harmful mutations within populations. This ability to correct errors helps ensure that beneficial variations can arise and be preserved while deleterious changes are minimized. In cancer biology, understanding how mismatch repair functions and its failure can provide insights into tumorigenesis and highlight potential therapeutic targets for cancers characterized by defective DNA repair mechanisms.

Related terms

DNA Polymerase:

An enzyme responsible for synthesizing new DNA strands during replication, also involved in proofreading and correcting errors.

Mutagen: An agent, such as chemicals or radiation, that causes changes or mutations in DNA, increasing the likelihood of mismatches during replication.

Heteroduplex: A DNA molecule containing strands from different sources or species, often used in studies of DNA mismatch repair mechanisms.