Two chains of DNA twist around each other to form a DNA double helix with the phosphate-sugar backbone spiralling around the outside, and the bases pointing inwards with <answer>adenine</answer> base pairing to thymine and guanine to cytosine. The specificity of base pairing occurs because <answer>adenine</answer> and thymine align form two hydrogen bonds, whereas cytosine and guanine form three hydrogen bonds. The two strands in a double helix must therefore be complementary, with their sequence of bases matching such that the <answer>adenine</answer>s of one strand are paired with the thymines of the other strand, and so on.:4.1
What base pairs with thymine?
adenine