In DNA, which base is complementary to guanine?

a. andenine

b. thymine

c. cytosine

d. guanine

Guanine is complementary to Cytosine.

Explanation:

The DNA molecule is made up of different components one of them is pairing of nitrogenous bases. The nitrogenous bases are the A, G, C, T. The A, G are the purine and C, T is the pyrimidine.

The A pairs with T by double hydrogen bond, and C pairs with G by a triple hydrogen bond. Thus the helix is arranged in antiparallel order.

The pairing of nitrogenous bases obeys Chargaff's rule. According to this rule, the combination of adenine and thymine is approximately equivalent to the combination of guanine and cytosine.

If the DNA bases do not obey this rule then the helical structure can't be possible. The pairing of purine, purine, and pyrimidine, pyrimidine results too short and too broad helix. Thus proper order of the helix can't be possible.

This is the very reason A double bonds with T and C triple bonds with G.