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In genetics, floxing refers to the sandwiching of a piece of DNA sequence (which is then said to be floxed) between two lox P sites. The terms are constructed upon the phrase "flanking/flanked by lox P sites". Recombination between lox P sites is catalysed by Cre recombinase. Depending on the placement of lox P sites, floxing a gene allows it to be deleted (knocked out), inserted (knocked in), translocated or inverted in a process called Cre-Lox recombination.

Floxed genes can be used to produce tissue-specific knockouts. For example, Cre recombinase under the control of alpha-myosin heavy chain or Glial fibrillary acidic protein promoter results in the floxed gene to be inactivated in the heart or astrocytes respectively. Further, these knockouts can be inducible. In several mouse studies, tamoxifen is used to induce the Cre recombinase. In this case, Cre recombinase is fused to a portion of the mouse estrogen receptor (ERTM) which contains a mutation within its ligand binding domain (LBD). The mutation renders the receptor inactive, which leads to incorrect localization through its interactions with chaperone proteins such as heat shock protein 70 and 90 (Hsp70 and Hsp90). Tamoxifen binds to Cre-ERTM and disrupts its interactions with the chaperones, which allows the Cre-ERTM fusion protein to enter the nucleus and perform recombination on the floxed gene. Additionally, Cre recombinase can be induced by heat when under the control of specific heat shock elements (HSEs).

Relevance
The floxing of genes is essential in the development of scientific model systems as it allows the the expression of a gene to be manipulated in a specific tissue at any time chosen by the scientist. This means that researchers can have spatial and temporal control over gene expression. Moreover, animals such as mice can be used as models to study human disease. Therefore, Cre-lox system can be used in mice to manipulate gene expression in order to study human diseases and drug development. For example, using the Cre-lox system, researchers can study Oncogenes and Tumor Supressor genes and their role in development and progression of cancer in mice models.