High level of genetic variability among commercially available "inbred" Mongolian gerbils

Adult MON/Tum and Tum:(MON) gerbils were grafted with sibling ear skin of the same sex to assess the degree of homogeneity within strains. Similar percentages of the MON/Tum and Tum:(MON) strain grafts were rejected in less than 200 days (55.3 percent and 66.7 percent, respectively). This was a surprising finding since the breeder claims the Tum:(MON) strain is random bred and the MON/Tum strain is inbred and has been brother-sister mated for more than 20 consecutive generations. The median survival times of rejected grafts were similar for both strains.