Deoxyribonucleic acid (i/diˈɒksiˌraɪboʊnjʊˌkliːɪk, -ˌkleɪɪk/;DNA) is a molecule that carries most of the genetic instructions used in the development, functioning and reproduction of all known living organisms and many viruses. DNA is a nucleic acid; alongside proteins and carbohydrates, nucleic acids compose the three major macromolecules essential for all known forms of life. Most DNA molecules consist of two biopolymer strands coiled around each other to form a double helix. The two DNA strands are known as polynucleotides since they are composed of simpler units called nucleotides. Each nucleotide is composed of a nitrogen-containing nucleobase—either cytosine (C), guanine (G), adenine (A), or thymine (T)—as well as a monosaccharide sugar called deoxyribose and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. According to base pairing rules (A with T, and C with G), hydrogen bonds bind the nitrogenous bases of the two separate polynucleotide strands to make double-stranded DNA. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037, and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).
DNA² (Japanese: D・N・A² ～何処かで失くしたあいつのアイツ～, Hepburn: Dī En Ei Tsū: Dokoka de Nakushita Aitsu no Aitsu) is a science fiction manga series written and illustrated by Masakazu Katsura. It was serialized across Shueisha's Weekly Shōnen Jump magazine between 1993 and 1994, spanning a total of five tankōbon volumes.
DNA² was adapted into a 12-episode anime television series which ran on Nippon Television from October 7, 1994 to December 23, 1994. This was followed by a three-episode anime original video animation (OVA) in 1995. Produced by Madhouse and Studio Deen, the anime series was directed by Jun'ichi Sakata, whereas the character designer and animation director for the series was Kumiko Takahashi. DNA² has been broadcast in Japan by Animax, which has also aired the series across its respective networks worldwide, including its English-language networks in Southeast Asia and South Asia. All 15 episodes were licensed in North America by Central Park Media until their closing in 2009. The five volumes and box set are out-of-print. Discotek Media has since re-licensed the series for a DVD release in 2014.