FrT

FRT is an acronym used in several fields, with the two most common meanings in biology and medicine.

In genetics, FRT stands for the Flp recombinase target site. The FRT site is a specific DNA sequence recognized by the Flp recombinase enzyme, which originates from the yeast Saccharomyces cerevisiae. When two FRT sites flank a DNA segment, the Flp recombinase can catalyze recombination between them, leading to excision, inversion, or integration of the intervening sequence. The Flp/FRT system is used as a tool for conditional gene modification in organisms such as mice and cultured cells, enabling researchers to control gene expression in time or in specific tissues. The method is conceptually similar to the Cre/loxP system and is chosen based on experimental design and organism compatibility.

In oncology, FRT commonly stands for fractionated radiotherapy. This approach delivers the total prescribed radiation dose in multiple smaller fractions over several weeks, rather than a single large dose. Fractionation exploits differences in repair capacity between normal and tumor tissues to improve tumor control while limiting late toxicity. Typical fractions are around 1.8 to 2 Gy per session, five days a week, though schedules vary. Variants include hyperfractionation, accelerated fractionation, and hypofractionation, each aiming to optimize tumor control, normal tissue tolerance, and treatment duration.

Other uses of the acronym exist in different domains, but the two meanings above are among the most widely recognized in scientific literature.