What are the two classes of nitrogen bases found in nucleic acids?

What are the two classes of nitrogen bases found in nucleic acids?

• A. Amino acids, Nucleotides
• B. Bases, Sugars
• C. Nucleotides, Nucleosides
• D. Purines, Pyrimidines

Answer: (D)

Nitrogenous bases in nucleic acids come in two families: purines and pyrimidines. Purines have a two-ring structure and include adenine and guanine. Pyrimidines have a single-ring structure and include cytosine, thymine (in DNA), and uracil (in RNA). This classification is central because it underlies base pairing in DNA and RNA (A with T or U, and G with C) and helps explain the chemical differences that drive structure and replication. The other options describe different biomolecules or parts of nucleotides, not the two classes of bases themselves.

Nitrogenous bases in nucleic acids come in two families: purines and pyrimidines. Purines have a two-ring structure and include adenine and guanine. Pyrimidines have a single-ring structure and include cytosine, thymine (in DNA), and uracil (in RNA). This classification is central because it underlies base pairing in DNA and RNA (A with T or U, and G with C) and helps explain the chemical differences that drive structure and replication. The other options describe different biomolecules or parts of nucleotides, not the two classes of bases themselves.