which of the following has thymine as one of its nucleotides?  a.dna  b.rna
The shape of adenine is complementary to either thymine in DNA or uracil in RNA. Cytosine (C). Cytosine (C) is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2). The nucleoside of cytosine is cytidine.