As we have seen, inbreeding can reduce offspring fitness by exposing deleterious recessive alleles. However, some animal breeders practice generations of careful inbreeding within a family, or "line breeding," and surprisingly many of the line-bred animals, from champion dogs to prize cows, have normal health and fertility. How can it be possible to continue inbreeding for many generations without experiencing inbreeding depression due to recessive alleles? (Hint: Consider some of the differences between animal breeders and natural selection in the wild.) Generally, if a small population continues to inbreed for many generations, what will happen to the frequency of the deleterious recessive alleles over time?