Nucleotides can be further categorized depending on their nitrogen base as a _____ or _____

• A. pyrimidine
• B. purine or pyrimidine
• C. nucleobase type
• D. base pair

Answer: (B)

The nitrogenous bases in nucleotides fall into two families: purines and pyrimidines. This is how nucleotides are categorized based on the base they contain. Purines (adenine and guanine) have a two-ring structure, while pyrimidines (cytosine, thymine in DNA, and uracil in RNA) have a single ring. Therefore, a nucleotide is described as a purine nucleotide or a pyrimidine nucleotide. The other options don’t fit because a nucleotide isn’t categorized simply as a pyrimidine alone, base pairing describes how bases pair across strands rather than the type of nucleotide, and “nucleobase type” is too vague compared with the standard purine/pyrimidine distinction.