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.
Chordata, phylum Chordata-comprises true vertebrates and animals having a notochord. cephalochordate-fish-like animals having a notochord rather than a true spinal column. tunicate, urochord, urochordate-primitive marine animal having a saclike unsegmented body and a urochord that is conspicuous in the larva.. Any of numerous animals of the phylum Chordata, having at some stage of development a dorsal nerve cord, a notochord, and gill slits and including all vertebrates, the hagfishes, and certain marine animals such as the lancelets and the tunicates.