what structural problem prevents adenine from pairing with guanine

Question

anonymous · Answer

Specifically the hydrogen bonds won't match up. Adenine has two spaces for but guanine has three. Also both adenine and guanine are purines so they both have two rings which means that if they paired the middle of the DNA would have four rings which would make it bulge out and be unstable.

anonymous · Answer

Does this help you?

agreene · Answer

To be fair, the amount of energy released from bonding is the only thing that prevents them... thats why T>G transversions are so common (makes A-G base pairings)