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.
1 A notochord, a fairly stiff rod of cartilage that extends along the inside of the body. 2  Among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. 3  A dorsal neural tube.