The part of a nucleotide that differs among the different nucleotides is the nitrogenous base. In DNA, those bases are adenine, thymine, cytosine, and guanine ; in RNA, uracil replaces thymine.

Quick Scoop

A nucleotide has three main parts:

  • A phosphate group
  • A five-carbon sugar
  • A nitrogenous base

The sugar and phosphate stay the same in a given nucleic acid, while the base is what changes. That base is what gives each nucleotide its identity.

Easy way to remember

If you think of a nucleotide like a three-piece puzzle, the base is the piece that comes in different versions.

If you want, I can also give you a one-sentence answer you can copy into homework.