| Type | MGI:General | Description | intercrosses of homozygotes produce a reduced average litter size relative to intercrosses of heterozygotes (4.2 vs 7 in 15 litters) test matings of mutant males with wild-type females produce a normal litter size, whereas matings of mutant females with wild-type males generate a reduced average litter size (3.9 in 9 litters) |