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Remember that an animal is inbred if his parents are related: Fanimal = ½ * abetween parents. Parents are related if they have ancestors in common. The fewer generation generations away this common ancestor is, the more the parents are related. Offspring of a full brother and sister have an inbreeding coefficient of ½*0.5 = 0.25. The less two parents are related, the less the offspring is inbred. Some breeding organisations have regulations to avoid mating of close relatives. The Dutch Kennel Club (overall organisation of the various dog breeds in the Netherlands and in charge of pedigree registration of all registered purebred dogs), for example, has the regulation that no pedigree will registered for offspring of a bitch that was mated to her grandfather, her father, her brother, her son, or her grandson.
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