Which of the following statements about base pairing is incorrect?

Base pairing is the hydrogen-bonded pairing of two complementary heterocyclic bases in the double helix of DNA.

Base pairing in DNA occurs during replication, transcription, and translation.

In base pairing, adenosine pairs with thymine in DNA or uracil in RNA, while guanine pairs with cytosine. 

In base pairing, a purine base can be paired with another purine base.