The two individual strands of a double helix of DNA are held together by (note: adenine = A; cytosine = C; thymine = T; guanine = G)

Question

A. Two hydrogen bonds between A and T, and three hydrogen bonds between C and G

B. Three hydrogen bonds between A and C, and three hydrogen bonds between T and G

C. Two hydrogen bonds between A and G, and three hydrogen bonds between C and T

D. One hydrogen bond between the sugar phosphate backbones of each nucleic acid strand



E. hydrogen bonds between C1 and C5 of the sugars in adjacent nucleotides

Answer 1

Quantitatively, the GC pair is bound by three hydrogen bonds, while AT and AU pairs are bound by two hydrogen bonds.