Base Pairing in Nucleic Acids
DNA is double stranded (ds); the nucleotide nitrogenous bases on one DNA strand bind to the nitrogenous bases of another strand by complementary base pairing. Complementary base pairing is binding between nitrogenous bases guanine (G) and cytosine (C) and between adenine (A) and thymine (T). In the formation of dsDNA, the phosphate-sugar backbone twists right-handed as seen in the illustration below.
RNA is usually single stranded (ss).
Denaturation is the process of breaking the bonds between the bases and converting ds to ss.