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.
[edit on Wikidata] In animal anatomy, the notochord is a flexible rod made out of a material similar to cartilage. If a species has a notochord, it is, by definition, a chordate. The notochord lies along the anteroposterior (head to tail) axis, is usually closer to the dorsal than the ventral surface of the animal, and is composed of cells derived from the mesoderm.