Which of the following statements about base pairing in DNA is incorrect?

Purines always base pairs with pyrimidines.

Adenine binds to guanine.

Base pairs are stabilized by hydrogen bonds.

Base pairing occurs at the interior of the double helix.

Adenine binds to guanine.

Explanation:

Rules of the base pairing are:

A with T

Purine base, adenine (A) pairs with the pyrimidine base, thymine (T).

C with G

Pyrimidine base, cytosine (C) pairs with purine base, guanine (G).

(Option A is correct).

(Option B is incorrect).

Nitrogenous bases are positioned in the inside helix structure like the rungs of a staircase due to hydrophobic effect and are stabilized by hydrogen bonding.

(Option C and D is correct).