C57BL/6 mouse strains. This does raise questions about generalizability beyond the model.
Complex genetic strains have been derived from crossing a dozen or so different inbred strains, producing a population that is genetically as complex as a human population, Holmes said. These strains have a place in research for answering specific questions, such as the genetic basis of a particular phenotype. The choice of strain depends on the question being asked. When studying the mechanism of a disease or the effect of a drug, there is value in controlling the genetic background of the animals. It was also noted that the same strain of animal (e.g., C57BL/6) from different breeders can have both genetic and behavioral differences.