cDNA genes are a locus (or region) of DNA for functional transcript RNA or protein. An ELISA is used to detect the expressed protein in biological fluids, serum, saliva.The receptors are ligand binding factors of type 1, 2 or 3 and protein-molecules that receive chemical-signals from outside a cell. When such chemical-signals couple or bind to a receptor, they cause some form of cellular/tissue-response, e.g. a change in the electrical-activity of a cell. In this sense, am olfactory receptor is a protein-molecule that recognizes and responds to endogenous-chemical signals, chemokinesor cytokines e.g. an acetylcholine-receptor recognizes and responds to its endogenous-ligand, acetylcholine. However, sometimes in pharmacology, the term is also used to include other proteins that are drug-targets, such as enzymes, transporters and ion-channels.
