Genetics load.

Genetic Load
One of the most fundamental misconceptions is that most of the individuals in a normal population do not carry genes for genetic diseases. Starting with this assumption, many breeders argue that it should be possible to breed animals with a desired conformation while avoiding undesirable traits. They will concede that some unfortunate individuals do carry recessive genes for these traits, but believe that if they choose their breeding stock carefully, they can avoid the problems that others are having. If problems do show up, it is due to "bad luck", the lack of direct genetic…