This diagram depicts the chemical structure of pyrimidine, a six-membered aromatic ring with two nitrogen atoms at positions 1 and 3 (highlighted in blue ... These nucleotides can then be further ...

highlighting the numbering of the carbon and nitrogen atoms. The purine structure consists of a pyrimidine ring (positions 1 to 6) fused to an imidazole ring (positions 7 to 9). Adenine and guanine, ...

In addition to the five nitrogenous bases—adenine ... team observed that the ratio of purines (adenine and guanine) to pyrimidines (cytosine, thymine and uracil) was much lower in the Bennu ...