Meiotic mapping identifies <i>Tyro3</i> as a candidate modifier.

<p>Haplotype map of chromosomes (rows) from 437 offspring of a backcross. Only chromosomes originating from a heterozygous parent are depicted. Black indicates a B6 allele, gray a 129 allele, and white an unscored marker. Retinal phenotyping (at right) localized the modifier between rs3669873 and rs3144592, a region of 2,099,167 bp (GRCm38 assembly). Marker rs27424653 (bold) is in an intron of <i>Tyro3</i>, which lies completely within and near the middle of the critical interval.