If the cassette has been successfully flipped out the internal LacZ PCR would be expected to fail, but the mutant-specific PCR would be expected to still amplify a band in mutant mice, as it is 5’ to the first FRT site. In homozygous mutant mice the wild type PCR would be expected to work again but will be approximately 200bp larger than in wild type animals. Heterozygous animals should show two WT bands; the normal sized one and the larger one.

Note: We have not yet verified such experiments to confirm these observations, this is in progress.