- If you are crossing two genetically modified lines together(such as a floxed or conditional line with a Cre line), you should consider testing some of the initial offspring to determine if you have the background strain of interest.

- Consider testing the genetic integrity of your colonies at one or more of the following points, depending on your use case:

• When introducing new breeders.
• When ensuring a lack of genetic contamination is critical, i.e. at the beginning
• and/or end of your study.
• Routinely spot-checking individuals from each of your litters to ensure the
• genetic background is free from contamination.
• To increase the speed of a backcrossing program (via speed congenics/marker assisted breeding).