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.
Answers. Best Answer: 1) The notochord is the defining structure of the phylum Chordata, which includes all vertebrates. In its mature state, the notochord is a rod of large cells constrained by a thick extracellular sheath and positioned between the developing spinal cord and gut.nswers. Best Answer: 1) The notochord is the defining structure of the phylum Chordata, which includes all vertebrates. In its mature state, the notochord is a rod of large cells constrained by a thick extracellular sheath and positioned between the developing spinal cord and gut.