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. Lacking a backbone or spinal column; not vertebrate. 2. Of or relating to invertebrates: invertebrate zoology. n. An animal, such as an insect or mollusk, that lacks a backbone or spinal column.nvertebrate. n. 1. (Zoology) any animal lacking a backbone, including all species not classified as vertebrates. adj. 2. (Zoology) of, relating to, or designating invertebrates.