mispair

Mispair refers to an incorrect pairing between two biological partners, most commonly involving nucleic acids or protein subunits. In genetics and molecular biology, mispairs are mismatches where a nucleotide pairs with a non-complementary partner, rather than the intended base pair.

In DNA, mispairing occurs when incorrect nucleotides are incorporated opposite the template during replication or repair. Common causes include tautomeric shifts, chemical modifications, or DNA damage that alter base-pairing properties. Mismatches can produce point mutations if left unrepaired. Cells counter mispairs with proofreading activity by DNA polymerases and with mismatch repair systems that recognize and correct irregular base pairs after replication.

Mispairing also occurs during transcription and translation. RNA polymerases can occasionally insert the wrong nucleotide opposite the DNA template, generating RNA with errors. In protein synthesis, codon-anticodon mispairing at the ribosome can lead to incorporation of an incorrect amino acid, potentially altering protein function. The translation machinery tolerates some near-cognate pairings, but proofreading mechanisms and cellular quality control work to minimize functional errors.

In protein assembly and the immune system, mispairing can refer to incorrect pairing of subunits or chains. For antibodies, mispairing of heavy and light chains from different alleles or incorrect pairing during V(D)J recombination can yield nonfunctional or self-reactive molecules. Such mispairs are typically subject to cellular quality control and selection processes.

In research and biotechnology, controlling mispairing is important for accuracy in sequencing, gene editing, and the design of nucleic-acid–based therapeutics. Understanding mispairing helps explain mutation rates, protein fidelity, and the reliability of molecular assays.