In DNA structure, which pair of nitrogenous bases are classified as purines?

• A. Guanine and cytosine
• B. Adenine and thymine
• C. Adenine and guanine
• D. Cytosine and thymine

Answer: (C)

Verified step by step guidance

1. Recall that nitrogenous bases in DNA are divided into two categories based on their structure: purines and pyrimidines.
2. Understand that purines have a two-ring structure, while pyrimidines have a single-ring structure.
3. Identify the purines in DNA as adenine (A) and guanine (G), both of which have the characteristic two-ring structure.
4. Recognize that cytosine (C) and thymine (T) are pyrimidines, each with a single-ring structure.
5. Therefore, the pair of nitrogenous bases classified as purines in DNA are adenine and guanine.