purine pyrimidine


Adenine and guanine are purines and cytosine, uracil, and thymine are pyrimidines.
Left - purine (smaller molecule with bigger name) and (right) pyrimidine (larger molecule with smaller name)
grey - carbon / white - hydrogen / blue - nitrogen
Labels: adenine, cytosine, guanine, purine, pyrimidine, thymine, uracil
T U mismatch

thymine (T) and uracil (U) differ only in the CH3 group on T, and may be mismatched.
Labels: T U mismatch, thymine, uracil