Genealogy of the C.D2-Pnd strains. Backcross progeny between BALB/c and (BALB/c × DBA/2) F1 hybrids that contained DBA/2 alleles of distal Chr 4 markers were selected to create C.D2-MIA mice. At the N10 generation the C.D2-MIA mouse was heterozygous for all loci from Ifna to D4Mit254. Markers proximal to Ifna were homozygous C/C (BALB/c). At the N11 generation, recombinants near the Nppa locus were selected for further breeding to create the C.D2-Pnd4 and seven strains of mice. These mice were further bred to BALB/c to create additional recombinants in the distal Chr 4 region near Nppa to create the C.D2-Pnd4A,4C,7A and 7B strains.