RESULTS. Major QTLs were discovered near the centromere of chromosome 5 (Eyel: genomewide P < 0.005) and on proximal chromosome 17 near the mast cell protease 6 gene (Eye2, P < 0.05). Both QTLs have significant effects on eye size, lens weight, and retinal area. The DBA/2J alleles at Eyel and Eye2 are partially dominant and increase eye weight by as much as 1.0 mg. Analysis of 183 F2 progeny confirmed and refined the chromosomal assignments of both Eyel and Eye2.