Norgen’s Homologous Recombination Assay Kit provides a rapid and sensitive tool for measuring the efficiency of homologous recombination in both bacterial and mammalian cells. The kit consists of 5 components: (1) dl-1 plasmid, (2) dl-2 plasmid, (3) positive control plasmid, (4) assay primers mixture, and (5) universal primers mixture. The assay is based on the co-transformation of the two dl plasmids into bacterial cells followed by the isolation of plasmid DNA and quantification of the homologous recombination efficiency through qPCR. In addition, PCR can be used for qualitative analysis of the recombination efficiency. The primer mixture provided with the kit is designed to amplify only the homologous recombination product but not the dl plasmids (dl-1 or dl-2). The two plasmids can be co-transfected into mammalian cells, then the DNA can be isolated and the homologous recombination efficiency can be assayed by qPCR (or PCR). In addition, the efficiency of homologous recombination can be assessed in bacteria by blue/white screening using X-gal. The provided positive control contains the functional LacZ sequence and can be used as a positive control for the plasmid DNA isolation efficiency (after transformation or transfection) or PCRs. The use of PCR-based homologous recombination assay enhances the sensitivity and eliminates the need for labor intensive screening by using traditional protein expression and staining techniques and is suitable for high throughput screening studies.  The kit is designed to perform 200 transformations or 24 transfections.