What is the structure and function of DNA?

DNA (deoxyribonucleic acid) is a double helix composed of units called nucleotides. Each nucleotide is composed of a single deoxyribose sugar, a phosphate group and one of four nitrogen bases. The 4 bases are adenine, thymine, guanine, and cytosine. Together they form the coded language that creates the human body by being the recipe from which proteins are synthesised.