Construction of a DBA/2.Fv-2r congenic strain. Apparent lethality of the homozygous Fv-2r genotype: brief communication.

From the (C57BL/6 X DBA/2)F1 cross, 13 serial backcrosses to the DBA/2 parental mouse strain were bred with selection by progeny testing in each generation for the Fv-2s/Fv-2r heterozygous genotype. Intercrossing heterozygotes of the 13th backcross generation produced no Fv-2r/Fv-2r homozygotes. Homozygosity for the Fv-2r allele thus appeared to be lethal on a DBA/2 background and in the absence of protector gene(s) of the C57BL strain.