Nucleoside is formed by a N-glycosidic linkage between nitrogenous base and pentose sugar. Phosphate group is attached to 5'-OH of a nucleoside through phosphoester bond. Two nucleotides are linked to form dinucleotide by a phophodiester bond. Therefore if there are 198 phosphodiester bonds in the DNA molecule then the number of base pairs will be two more than the bonds as the nucleotides present on the ends of the polynucleotide chain will also be counted.