Cre-Lox recombination is a site-specific recombinase technology, used to carry out deletions, insertions, translocations and inversions at specific sites in the DNA of cells. It allows the DNA modification to be targeted to a specific cell type or be triggered by a specific external stimulus.

Cre (Cre recombinase) is one of the tyrosine site-specific recombinases (T-SSRs) including flipase (Flp) and D6 specific recombinase (Dre) [1,2]. it was discovered as a 38-kDa DNA recombinase produced from cre (cyclization recombinase) gene of bacteriophage P1 [3,4,5,6].

Therefore, the Cre/loxP system allows for making a series of DNA sequence rearrangements, which helps to build one of the most versatile genetic tools in mice (2,3). The major application of Cre/loxP system is generation of cell- or tissue-specific conditional knockout alleles in mice (4).

The Cre enzyme identifies pairs of loxP sites (arrowheads), which flank (flox) the DNA, and catalyzes reciprocal DNA recombination between the two sites to excise a small piece of DNA.