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.
In vertebrates, the dorsal nerve cord differentiates into the brain and spinal cord. 2. A flexible rod, the notochord, forms on the dorsal side of the primitive gut in the. early embryo and is present at some developmental stage in all chordates.