Which bases are classified as standard nucleic acid purine bases?

The identification of standard nucleic acid purine bases centers on understanding the components of nucleotides that comprise RNA and DNA. In nucleic acids, purines are one of the two types of nitrogenous bases, with the other being pyrimidines.

The two standard purine bases commonly found in nucleic acids are adenine (A) and guanine (G). These bases are characterized by their two-ring structure, which distinguishes them from pyrimidines that only have a single-ring structure. Adenine and guanine play crucial roles in various biological processes, including the encoding of genetic information and the energetic transactions of biochemistry, such as ATP.

In the context of the other options, the bases provided include pyrimidines or elements that do not qualify as standard purine bases. Cytosine (C), Uracil (U), and Thymine (T) are all pyrimidines, and therefore do not fit the criterion of being purines. Additionally, options that include bases like W (which typically represent a mixed base) do not fit the definition of standard nucleic acid purines.

Thus, the correct answer, which identifies adenine and guanine as the standard purine bases, aligns perfectly with established classifications