The genetic background of genetically engineered mice can influence phenotype.

Inattention to a mutant’s genetic background can substantially confound research results. Each strain of mice has unique background alleles that may interact with and modify the expression of a mutation, transgene, or other genetic insert.

To ensure the validity and reproducibility of a study, all animals must be genetically identical (except for the gene or modification of interest). Genetic Monitoring is a single nucleotide polymorphism (SNP)-based testing service that can be used to ensure this genetic purity by testing the integrity of inbred and congenic strains.