The DNA molecule is a chain of repeating nucleotides. Each nucleotide is made up of a nitrogenous base, a sugar molecule, and a phosphate group. These nucleotides are linked together in a specific sequence to form a long chain, which is the DNA molecule. The nitrogenous bases in the nucleotides are adenine (A), thymine (T), cytosine (C), and guanine (G), and the sequence of these bases determines the genetic information stored in the DNA molecule.