Purines are composed of which bases?

Prepare for the Campbell Biology Concepts and Connections test. Hone your skills with multiple choice questions, flashcards, hints, and thorough explanations. Ace your exam effortlessly!

Multiple Choice

Purines are composed of which bases?

Explanation:
Purines are a class of nitrogenous bases with a two-ring structure. The purines are adenine and guanine, while cytosine and thymine (and uracil in RNA) are pyrimidines with a single ring. This distinction explains why adenine and guanine are listed as the purines. In DNA, purines pair with pyrimidines, so thymine pairs with adenine and cytosine pairs with guanine. The other options mix purines with pyrimidines or list two pyrimidines, so they aren’t both purines.

Purines are a class of nitrogenous bases with a two-ring structure. The purines are adenine and guanine, while cytosine and thymine (and uracil in RNA) are pyrimidines with a single ring. This distinction explains why adenine and guanine are listed as the purines. In DNA, purines pair with pyrimidines, so thymine pairs with adenine and cytosine pairs with guanine. The other options mix purines with pyrimidines or list two pyrimidines, so they aren’t both purines.

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