Genetic drift and undetected cross-colony contamination silently compromise experimental reproducibility over successive breeding generations, and are easy to miss with visual inspection alone.

Catch genetic drift and contamination before it affects experiments: 1) Genotype foundation-stock breeders annually using a large SNP marker panel (2,000+ markers), rather than relying on visual/phenotypic inspection alone. 2) Also randomly sample and genotype mice from the production colony, not just foundation breeders, to catch contamination introduced downstream. 3) A core subset of around 52 markers, informative across 100+ strains, is sufficient to flag most contamination events and can be used as a faster routine screen. 4) Remove any animals flagged by the SNP panel from the breeding colony immediately rather than waiting for a phenotypic anomaly to appear.