This is a Taqman based screen in which the target primers/probe are developed within a unique wildtype region that is replaced or interrupted via homologous recombination of both vector homology arms.  

The data is analyzed via a multiplexed relative cycle threshold method in duplicate in which the target reaction Ct is compared to an endogenous reference reaction Ct (Y chromosome).  A delta Ct is plotted and cluster analysis is applied in which a clear separation of cluster groups are indicative of 2 copy/cell (non targeted) and 1 copy/cell (targeted) clones as compared to known wildtype controls.