Missparning

Missparning, also called mispairing, is the incorrect pairing of genetic material during cellular processes. In a broad sense, it refers to two related phenomena: mispairing of DNA bases during replication and mispairing of chromosomes during meiosis.

Mispairing during meiosis can occur when homologous chromosomes fail to align properly due to structural differences or repetitive sequences. This can produce unequal crossing over or recombination between non-homologous regions, leading to chromosomal rearrangements such as deletions, duplications, or translocations, and to unbalanced gametes. Such errors can cause miscarriages, congenital abnormalities, or infertility.

Mispairing at the nucleotide level occurs when non-complementary bases are paired during replication. DNA polymerases have proofreading activity, and post-replication mismatch repair pathways correct most mispairs. If unrepaired, base mispairs become permanent mutations, contributing to genetic variation and disease risk. Factors such as DNA damage, repeats, and chemical exposures increase mispairing rates.

In research and breeding, understanding mispairing informs genome stability, mutation rates, and strategies to maintain fidelity in cloning and genetic engineering.