Footprinting
A technique by which one identifies a protein binding site on cellular DNA. The presence of a bound protein prevents DNase from"nicking" that region, which can be detected by an appropriately designed gel.

Fragment
See restriction fragment.

Frameshift mutation
A mutation that changes the reading frame of an mRNA, either by inserting or deleting nucleotides.

Friable
A term commonly used to describe a crumbling or fragmenting callus. A friable callus is easily dissected and readily dispersed into single cells or clumps of cells in solution.

Founder animal
In transgenesis research, an organism that carries a transgene in its germ line and    can be used in matings to establish a pure breeding transgenic line, or one that acts as a breeding stock for transgenic animals.

Founder principle
The possibility that a new, small, isolated population may be genetically different from the parent population, because the founding individuals (being a small, random sample from the large, parent population) could be quite different from typical members of the parent population.

Fusion gene
A hybrid gene created by joining portions of two different genes (to produce a new protein) or by joining a gene to a different promoter (to alter or regulate gene transcription).

Fusion protein
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 mad 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. See affinity tag; fusion biopharmaceutical.