Structure of RNA and DNA. Illustration of the structure and nucleotide bases of the genetic molecules ribonucleic acid (RNA, left) and deoxyribonucleic acid (DNA, right). The nucleotide bases are cytosine (C), guanine (G), adenine (A), thymine (T) and uracil (U). DNA is the genetic material that controls the growth and development of all living organisms. It is a double helix, with two spiralling sugar phosphate strands joined by nucleotide base pairs (coloured bars). The order of these nucleotides base pairs forms the genetic code. RNA is vital for the coding, decoding, regulation, and expression of genes.