<prompt> Common substrate for purine and pyrimidine synthesis are all except ?GlutamineGlycineAspaateCarbon dioxide  <response>: Ans. is b i.e., Glycine Glutamine, aspaate aspaic acid and CO, are preursors for both purines pyrimidines.In de novo synthesis, purine ring is formed from variety of precursors is assembled on ribose-5-phosphate. 