A molecule produced by a gene that carries out biological functions.

Related
RNA
Ribonucleic acid is the cell’s copy of our genetic material known as DNA. The primary role of RNA is to convert the information stored in DNA into proteins which carry out cellular functions.
ELISA
The enzyme-linked immunosorbent assay (ELISA) is an immunological assay commonly used to measure antibodies, antigens, proteins and glycoproteins in biological samples.