the naturally-occurring modified bases , n6-methyladenine , n4-methylcytosine , and 5-methylcytosine were chemically introduced in place of the adenine or cytosine in the decadeoxyribonucleotides containing recognition sequences of bgl ii , sau 3ai , mbo i and mfl i .
C0049308
5-methylcytosine
C0010843
cytosine