of the dogs under human reproductive control into breed categories based on their DNA sequences. Dogs are grouped into the following eight breed categories of herding, hound, nonsporting, sporting, terrier, toy, working and miscellaneous. As some health problems are hereditary, knowing the common health problems that are related to the type of dog you are trying to breed can be used to improve its successors by mating the dam with a sire who has a pedigree that lacks these health issues. By studying a dog's pedigree, you can avoid breeding dogs known to carry a dominant or recessive genetic mutation as they could pass this onto their offspring. Breeding Most mating done by purebred breeders is linebreeding which is the mating of animals of different families within the same breed to bring in desirable traits that are not present in the original animals. Unlike commercial producers, purebred breeders cannot use crossbreeding as it would dilute the breed's purity, resulting in a mixed breed dog. Health checks and genetic screenings are done prior to mating as well. The age at which dogs fully mature varies by breed, however there are stringent guidelines that the parents should not be bred until they are mature enough. For example, the AKC does not allow the registration of a litter from a dam whom at the time of mating was less than 8 months of age or more than 12 years, or of a sire that was less than 7 months or more than 12 years of age. References See also Animal husbandry Breed standard Breed type Crossbreeding Dog Dog breed Dog Crossbreed/Hybrid Dog type Dog breeding