During mismatch repair, why is it necessary to distinguish between the template strand and the newly made daughter strand? Describe how this is accomplished.

Key Concepts

Mismatch Repair

Mismatch repair is a cellular mechanism that corrects errors that occur during DNA replication, specifically when incorrect nucleotides are incorporated into the newly synthesized strand. This process is crucial for maintaining genetic stability and preventing mutations that could lead to diseases, including cancer. The system identifies and repairs mismatches to ensure the fidelity of genetic information passed on during cell division.

Template Strand vs. Daughter Strand

In DNA replication, the template strand is the original strand of DNA that serves as a guide for synthesizing a new complementary strand, known as the daughter strand. Distinguishing between these two strands is essential during mismatch repair because the template strand is the correct reference for what the sequence should be, while the daughter strand may contain errors that need correction. This differentiation is typically achieved through the presence of methylation marks on the template strand in prokaryotes or through the age of the strands in eukaryotes.

Strand Discrimination Mechanisms

Strand discrimination mechanisms are processes that allow cells to identify which strand of DNA is the template and which is the newly synthesized daughter strand. In bacteria, this is often accomplished through the methylation of adenine residues in the template strand, which is not immediately present in the newly synthesized strand. In eukaryotes, the distinction can rely on the timing of replication and the presence of specific proteins that recognize and bind to the newly synthesized strand, facilitating accurate repair.