Construction of a D2.B6-Fv-2r congenic mouse strain: nonlethality of the homozygous Fv-2' genotype.

Starting from the (C57BL/6 x DBA/2)F1 generation (Fv-2s/Fv-2r), 16 serial backcrosses to mice of the parental DBA/2 strain (Fv-2s/Fv-2s) were bred. In each generation, heterozygous Fv-2s/Fv-2r segregants were selected and backcrossed with a DBA/2 parent. In the 16th generation, Fv-2s/Fv-2r heterozygotes were intercrossed, and Fv-2r/Fv-2r homozygotes were selected for interbreeding to establish a congenic strain, D2.B6-Fv-2r. The successful establishment of this congenic strain is in contrast with previous findings suggesting that homozygosity for the Fv-2r allele might be a lethal genotype on the DBA/2 genetic background. At least 10 centimorgans of Fv-2r-linked chromosomal material originating from the C57BL/6 ancestor remains in the D2.B6-Fv-2r genome, as shown by the continued presence of C57BL/6 alleles at the flanking Kfo-1 and Bgl-s loci. The observed recombination frequency for the intervals between Fv-2 and Bgl-s was 6.8%.