DNA, or deoxyribonucleic acid, is the hereditary material in all living organisms. It carries the genetic instructions used in growth, development, functioning, and reproduction. DNA is structured as a double helix, consisting of two long strands of nucleotides twisted around each other, with sequences of four bases: adenine (A), thymine (T), cytosine (C), and guanine (G). The sequence of these bases encodes the information necessary for building proteins, which perform most life functions. DNA is found in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells, making it essential for life as we know it.