Here's a breakdown:

* DNA is a long chain of molecules that holds the genetic instructions for an organism.

* Nucleotides are the building blocks of DNA.

* Each nucleotide consists of three parts:

* A sugar molecule (deoxyribose in DNA)

* A phosphate group

* A nitrogenous base (adenine, guanine, cytosine, or thymine)

These nucleotides link together in a specific sequence to form the DNA molecule, and the order of the bases determines the genetic information encoded within.