The correct answer is (d). Guanine is a purine base.
Purine bases are nitrogenous bases that are found in DNA and RNA. They are double-ringed molecules that are made up of a pyrimidine ring and an imidazole ring. Purines are essential for the structure and function of DNA and RNA. They are also involved in the regulation of gene expression.
Thymine, cytosine, and uracil are pyrimidine bases. They are single-ringed molecules that are made up of a pyrimidine ring and a pyrimidine ring. Pyrimidine bases are also found in DNA and RNA. They are involved in the formation of base pairs.
Thymine is complementary to adenine. Cytosine is complementary to guanine. Uracil is complementary to adenine in RNA.
Purine bases are larger than pyrimidine bases. They are also more hydrophobic than pyrimidine bases. This difference in size and hydrophobicity is important for the structure and function of DNA and RNA.
Purine bases are essential for life. They are involved in the storage and transmission of genetic information. They are also involved in the regulation of gene expression.