An otter breeder discovers several pups with pointy ears. She attempts to establish a bunch of pointy eared-otters by selling off all normal-eared pups and breeding only the pointy-eared pups. Ten generations later, she is frustrated to find that crosses between two of her pointy-eared otters still produce 70% curled and 30% normal pups. Identical twin pups invariably have the same kind of ears. She also notes that her newly formed breed is not as fertile as expected.
a) Excluding any environmental factors What is a likely explanation for her results?