A–C, To ascertain the tippy gene, an intersubspecific intercross between tip/+ heterozygous mice and Molf/Ei mice was performed (A). DNA from affected F2 mice was typed for polymorphic markers, localizing the tippy locus to a 1.0 cM/2.1 Mb region on distal chromosome 9 between SNP markers rs33627650 and rs3714504 (B, labeled in red). Haplotype analysis of 211 affected F2 mice defining the maximal critical interval harboring the tippy gene on chromosome 9 (C). Haplotypes for each marker are shown as columns with numbers of mice represented underneath. White boxes indicate C3H homozygous loci, white striped boxes indicate B6/C3H heterozygous loci, black striped boxes indicate B6 homozygous loci, and black boxes denote C3H or B6/Molf heterozygous loci.