DNA model and a genetic sequence. Printout of the genetic code of a single strand of DNA (deoxyribo- nucleic acid). Also seen is a model of DNA, which comprises two spiralling paired strands of sugar phosphates that are linked by nucleotide base pairs. There are four bases: adenine (A), thymine (T), guanine (G) and cytosine (C), which form the struts of the DNA molecule. The arrangement of the bases along a helix of DNA is the genetic code for protein synthesis and the functioning & growth of every living organism. DNA is found in cell nuclei.