The four chemicals that make up DNA strands are called nucleotides. Each nucleotide consists of three parts:

1. Deoxyribose sugar: A five-carbon sugar molecule.

2. Phosphate group: A molecule containing phosphorus and oxygen.

3. Nitrogenous base: This is the part that varies and determines the nucleotide's identity. There are four nitrogenous bases in DNA:

* Adenine (A)

* Guanine (G)

* Cytosine (C)

* Thymine (T)

These four nucleotides, combined in different sequences, form the genetic code that makes up DNA.