genetics what is a base
Apart from adenine (A), cytosine (C), guanine (G), thymine (T) and uracil (U), DNA and RNA also contain bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine (m 5 C).In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine (Ï), dihydrouridine (D), inosine (I), and 7-methylguanosine (m 7 G).ther bases, that do not function as normal parts of the genetic code, are termed non-canonical. In normal spiral DNA the bases form pairs between the two strands: A with T and C with G. Purines pair with pyrimidines mainly for dimensional reasons-only this combination fits the constant width geometry of the DNA spiral.