What structural problem prevents adenine from pairing with g

What structural problem prevents adenine from pairing with guanine?

A. The bases are both short.

B. They lack phosphate groups.

C. They lack the deoxyribose group.

D. The bases are both long.

Solution

Ans.) D. The bases are both long.

(Adenine and guanine both are purines; they never pair to each other. This is due to the presence of three hydrogen bond in guanine while there is only two hydrogen bond present in adenine.)