Genetic linkage map of the locus and molecular analysis of Madh5 transcripts in f/f, f/+, and control mice. (A) Linkage map of the f locus on mouse chromosome 13. The position of the markers on chromosome 13 according to NCBI m33 mouse genome assembly is indicated. The number of recombinants in each interval among the scored intercross F2 progeny is indicted at the right. The positions of Madh5 and Sfxn1 are shown. (B) The coding region of the Madh5 was cloned by RT-PCR of spleen RNA from the indicated mice. The arrows indicate the position of the wild-type and mutant mRNAs. The asterisk indicates a nonspecific background band. The exon structure of the wild-type and f/fmRNAs is indicated at the right. The f/fmouse shown here is an example of a mutant mouse that expresses very little wild-type Madh5 mRNA.