Mutations introgressed on different backgrounds result in different phenotypes. For example, a diabetes mutation (Leprdb) on a C57BL/6J background results in obesity with transient diabetes, but on a C57BLKS/J background, the same mutation results in obesity with overt diabetes. Likewise, an obesity mutation (Lepob) on the C57BL/6J background results in obesity with transient diabetes, but results in obesity with overt diabetes when transferred to the C57BLKS/J background.
As the number of mouse strains and substrains increases, attention to genetic background will be increasingly more important. Otherwise, research results will either be confounding or unreliable (Gerlai 2001; Linder 2001; Wolfer et al. 2002). Although a fair amount of confounding research is probably never reported, examples of reported studies include the following:
Remember that linked genes can differ between experimental models and controls and that, in some cases, it may be a good idea to test alleles on several backgrounds. Try to follow the recommendations of the Banbury Conference (Silva et al. 1997):
