A polypeptide made from a recombinant gene that contains portions of two or more different genes. The different genes are joined so that their coding sequences are in the same reading frame: the genetic apparatus reads the gene fusion as a single gene, and so produces a fusion protein. Also known as hybrid protein or chimeric protein. These proteins are used:

- to add an affinity tag to a protein;

- to produce a peptide as part of a larger protein, which is then cut up after it has been made by cloning;

- to produce a protein with the combined characteristics of two natural proteins; or

- to produce a protein where two different activities are physically linked.