<prompt> All of the following are true about the structure of bases found in nucleotides, EXCEPTPurine ring is nine-memberedPyrimidine ring is six-memberedPurine and pyrimidine rings are heterocyclic in natureImino and lactim form of purine bases are more stable  <response>: Purine and Pyrimidine Purines and pyrimidines are nitrogen-containing heterocycles Purines and pyrimidines exhibit tautomerism. The oxo and amino groups of purines and pyrimidines exhibit keto-enol and amine-imine tautomerism. Physiologic conditions strongly our the amino and oxo forms. Purine - 9 membered ring Pyrimidine - 6 membered ring 