Figure 1.

Genetic background variation in mouse strains, as shown by two adult mice with their pups. The C57BL/6J mouse (black coat) was crossed with a chimeric mouse (patchy coat), consisting of mutant C57BL/6J cells in a BALB/c white background. The offspring with a black coat color can then be screened for germline transmission of the mutant allele. Image: Ozgene Pty. Ltd.