Practice question

Ideal primers must remain linear to efficiently hybridize with template DNA. A hairpin structure arises when a primer contains internal self-complementary sequences that fold back, forming intra-molecular base pairing and a loop. This conformation sequesters primer, reduces effective concentration available for template binding, impedes polymerase extension, and lowers reaction efficiency. Primer design software therefore penalizes palindromic sequences, especially involving 3' end, and targets minimal self-complementarity. Avoiding hairpin formation ensures maximal accessibility and improves specificity, yield, and reproducibility of amplification, essential for diagnostics and cloning.