The part of the nucleotide that can differ in DNA is the nitrogenous base. DNA nucleotides contain one of four bases: adenine (A), thymine (T), cytosine (C), or guanine (G). The sequence of these bases along the DNA strand encodes genetic information, and their pairing (A with T, C with G) helps form the double-helix structure. The sugar (deoxyribose) and the phosphate backbone are constant across nucleotides, while the base varies, providing the genetic diversity.