deoxyribonucleic acid, desoxyribonucleic acid, DNA(noun) (biochemistry) a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix; associated with the transmission of genetic information.
But even adults don't often know what a notochord is. A notochord is a primitive beginning to the backbone. It appears in embryos as a small flexible rod made from cells from the mesoderm, which is one of the three layers of cells of embryos. Notochords are only found in the phylum chordata, a group of animals that includes humans.
Hemichordates are a group of organisms that show an affinity to the chordates, but are lacking some key characteristics of chordates. They include two groups.  Enteropneusta (acorn worms). These are 2 cm to 1.5 m long; marine in shallow waters, solitary, live in mud or vegetation; filter-feeders.