The purine structure consists of a pyrimidine ring (positions 1 to 6) fused to an imidazole ring (positions 7 to 9). Adenine and guanine, the two most common purines in DNA and RNA, share this core ...

Laying the Groundwork: Levene Investigates the Structure of DNA Meanwhile ... In other words, the total amount of purines (A + G) and the total amount of pyrimidines (C + T) are usually nearly ...

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). The remaining positions are occupied by ...

The novel feature of the structure is the manner in which the two chains are held together by the purine and pyrimidine bases. The planes of the bases are perpendicular to the fibre axis.