Adenine and guanine are purines, while thymine, cytosine and uracil are pyrimidines. RNA also contains adenine, guanine, and cytosine, but replaces thymine with uracil. Adenine and guanine are purines, cytosine and uracil are pyrimidines. The most common nitrogenous bases are adenine, cytosine, guanine, thymine, and uracil. Pyrimidines include thymine, cytosine, and uracil. Hypoxanthine is produced from adenine, xanthine from guanine, and uracil results from deamination of cytosine. Pyrimidine is a component of the nucleobases cytosine, uracil, and thymine. The shape of adenine is complementary to either thymine in DNA or uracil in RNA. A cytosine&colon;guanine pair is thus directly mutated to a uracil&colon;guanine mismatch. Thymine occurs only in DNA and uracil only in RNA. DNA contains thymine (T) while RNA contains uracil (U). Similarly, deamination of cytosine results in uracil. In RNA, thymine is replaced by the nucleobase uracil. RNA also contains the base uracil in place of thymine. Bisulfite sequencing relies on the conversion of every single unmethylated cytosine residue to uracil.