Not present in DNA -

Ans. is 'a' i.e., Uracil o Two types of bases are found in nucleotides : (i) purines and (ii) pyrimidines.Purines : Two major purine bases found both in DNAs as well as RNAs are (i) adenine (A) and (ii) guanine (G).Pyrimidines : Three major pyrimidine bases are (i) cytosine (C), (ii) Uracil (U) and (iii) Thymine (T). Cytosine and uracil are found in RNAs and cytosine and thymine are found in DNAs. Uracil is notfound in DNAs e and thymine is notfound in RNAs.Different major bases with their corresponding nucleosides and nucleotidesBaseRibon ucleosideRibonucleotideAdenine (A)Guanine (G)Uracil (U)Cytosine (C)AdenosineGuanosineUridineCytidineAdenosine monophosphate (.AMP)Guanosine monophosphate (GMP)Uridine monophosphate (UMP)Cytidine (Monophosphate) (CMP)BaseDeoxyribonucleosideDeoxyribonucleotideAdenineGuanineCytosineThymineDeoxyadenosineDeoxyguanosincDeoxy cytidineDeoxythymidineDeoxyadenosine monophosphate (dAMP)Deoxyguanosine monphosphate (dGMP)Deoxvcytidine monophosphate (dCMP)Deoxythymidine monophosphate (dCMP)