Multiple choice

Which of the nitrogenous bases are classified as purines?

  1. adenine and guanine

  2. adenine and thymine

  3. cytosine and guanine

  4. cytosine and thymine

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Purines are double-ring nitrogenous bases, which include adenine and guanine. Pyrimidines are single-ring bases, which include cytosine and thymine.