DNA is well known for its double helical structure. Two scientists named James Watson and Francis Crick first discovered this structure in 1953 using data from X-ray diffraction experiments.

The two strands of the helix are held together by hydrogen bonding as well as stacking interactions between the aromatic rings of the nitrogenous bases. These strong interactions make the double helical structure very stable. It’s also true, however, that the double helical structure has to be temporarily pulled apart when it’s time to transcribe the DNA into RNA. This is accomplished by an enzyme called helicase.