Table 1.

Aspects of laboratory animal quality and potential consequences of quality variation

Criteria categories	Criteria	Consequences of poor quality
Allele of interest	Genomic alterationa	Phenotypes associated with the wrong genetic alteration
	Functional consequences of mutation	Misinterpretation of phenotypes
Contamination with other alleles	Animal mix-up or incomplete breeding records	Phenotypes may be due to the wrong genetic alteration
Genetic background	Additional mutations fixed in closed colonies, genetic drift	Phenotypes due to the wrong genetic alteration or background
	Animal mix-up or incomplete breeding records	Phenotypes erroneously associated with genetic background or alteration
Hosted in mice and other environmental factors	Microbiota	The microbiota may modulate the observed phenotype in animals
	Pathogens	Observed phenotype is erroneously associated with a genetic alteration instead of being recognised as a consequence of a pathogenic infection
	Nutrition, husbandry conditions	Environmental factors are modulating the phenotype

^aSee Table 2 for quality control checks. The allele of interest may have been poorly validated initially or mutated subsequently