Mismatch repair

Definition

Mismatch repair is a cellular process that corrects errors that occur during DNA replication, specifically mispaired nucleotides. This mechanism is crucial for maintaining genetic stability by ensuring that the newly synthesized DNA strands match the original template strands. When mismatches are detected, specialized proteins identify and remove the incorrect base, allowing the correct base to be inserted, thus preserving the integrity of the genetic information.

5 Must Know Facts For Your Next Test

1. Mismatch repair primarily targets base pair mismatches that escape proofreading by DNA polymerase during replication.
2. The process involves several key proteins, including MutS, which recognizes mismatches, and MutL, which facilitates the repair process.
3. In bacteria, mismatch repair is critical for survival and genetic fidelity; defects can lead to increased mutation rates.
4. In eukaryotes, mismatch repair plays a role in preventing cancer by correcting replication errors before they can lead to mutations.
5. Defects in mismatch repair systems are associated with certain types of cancer, such as Lynch syndrome, highlighting its importance in genomic stability.

Review Questions

• How does mismatch repair differ from other DNA repair mechanisms like nucleotide excision repair?
  • Mismatch repair specifically corrects errors that occur during DNA replication by fixing mispaired bases, whereas nucleotide excision repair addresses larger DNA lesions caused by environmental factors like UV radiation. Mismatch repair involves detecting and repairing specific base pair mismatches using proteins like MutS and MutL. In contrast, nucleotide excision repair removes a short segment of DNA surrounding a damaged area before synthesizing a new strand to fill the gap.
• What are the implications of malfunctioning mismatch repair systems in eukaryotic cells?
  • Malfunctioning mismatch repair systems in eukaryotic cells can lead to an accumulation of mutations due to unresolved replication errors. This increase in mutation rates can disrupt normal cellular functions and contribute to cancer development. For example, individuals with defects in mismatch repair pathways have a higher risk of developing Lynch syndrome, which predisposes them to various cancers. Therefore, effective mismatch repair is vital for maintaining genomic integrity and preventing tumorigenesis.
• Evaluate the role of mismatch repair in maintaining genetic stability and its connection to cancer development.
  • Mismatch repair plays a critical role in maintaining genetic stability by correcting replication errors that can lead to mutations. When this system fails, the likelihood of accumulating mutations increases significantly, leading to genomic instability. This instability is a hallmark of cancer cells, as it allows for uncontrolled growth and adaptation. The connection between defective mismatch repair mechanisms and cancer development is evidenced by conditions like Lynch syndrome, where individuals experience higher incidences of colorectal and other cancers due to inherited mutations affecting their mismatch repair genes.

Related terms

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

Nucleotide Excision Repair: A DNA repair mechanism that removes bulky DNA lesions and replaces them with the correct nucleotides to maintain genome integrity.

Homologous Recombination: A process of genetic recombination where nucleotide sequences are exchanged between two similar or identical strands of DNA, often used in DNA repair.