Almost like how the combination of 0's and 1's encode the
programming for a computer, the DNA codes our genes (which
expressed as phenotypes) with a combination of nucleotide base
pairs: Adenine with Thymine, and Cytosine with Guanine.
These genes are expressed as proteins (E.G., for hair color) through the transcription of DNA into mRNA (which is necessary to make a protein template) and then translation from mRNA into protein (which first translates a group of three nucleotides (codons) into their respective amino acid, then binds the amino-acids together to form a polypeptide).