Editing Purebred (section)

==True breeding==
In the world of [[selective breeding|selective animal breeding]], to "breed true" means that specimens of an animal [[breed]] will breed true-to-type when mated like-to-like; that is, that the progeny of any two individuals of the same breed will show fairly consistent, replicable and predictable characteristics, or traits with sufficiently high heritability.<ref>{{cite book |doi=10.1016/B978-0-08-100099-1.00002-9 |chapter=What can animal models tell us about depressive disorders? |title=Modeling Neuropsychiatric Disorders in Laboratory Animals |date=2016 |last1=Hoffman |first1=Kurt Leroy |pages=35–86 |isbn=978-0-08-100099-1 }}</ref><ref>{{cite book|author1=Rieger, R. |author2=Michaelis, A. |author3=Green, M.M. |year=1968|title=A glossary of genetics and cytogenetics: Classical and molecular|url=https://archive.org/details/glossaryofgeneti00rieg |url-access=registration |publisher=Springer-Verlag|location=New York|isbn=9780387076683}}</ref> A puppy from two purebred dogs of the same breed, for example, will exhibit the traits of its parents, and not the traits of all breeds in the subject breed's ancestry.

Breeding from too small a gene pool, especially direct [[inbreeding]], can lead to the passing on of undesirable characteristics or even a collapse of a breed population due to [[inbreeding depression]]. Therefore, there is a question, and often heated controversy, as to when or if a breed may need to allow "outside" stock in for the purpose of improving the overall health and vigor of the breed.

Because pure-breeding creates a limited [[gene pool]], purebred animal breeds are also susceptible to a wide range of congenital health problems.<ref name="dogtown">{{cite video |title=Hurricane Hound |series=Dog-town |publisher=National Geographic Channel}}</ref> This problem is especially prevalent in competitive dog breeding and dog show circles due to the singular emphasis on aesthetics rather than health or function. Such problems also occur within certain segments of the horse industry for similar reasons. The problem is further compounded when breeders practice [[inbreeding]].<ref name="pde">{{cite video |title=Pedigree Dogs Exposed |medium=TV documentary |publisher=[[BBC]]}}</ref> The opposite effect to that of the restricted gene pool caused by pure-breeding is known as [[hybrid vigor]], which generally results in healthier animals.<ref name="dogtown" />