Practice question

Nucleic acid hybridization is stabilized by specific non-covalent interactions. Hydrogen bonding between complementary bases confers specificity and contributes enthalpy. Base stacking interactions arising from hydrophobic effects and pi-pi overlap of aromatic rings greatly stabilize the double helix. Ionic interactions mediated by monovalent cations like Na+ shield negative charges of phosphate backbones, reducing electrostatic repulsion and increasing duplex stability. Van der Waals forces, while present in any molecular association, are not considered a major distinct stabilizing force for hybrids in classical molecular biology curricula.