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marriage to a person belonging to a tribe or group other than your own as required by custom or law (同)intermarriage

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/10/06 12:50:38」(JST)

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Outcrossing or outbreeding is the practice of introducing unrelated genetic material into a breeding line. It increases genetic diversity, thus reducing the probability of an individual being subject to disease or reducing genetic abnormalities.^{[citation needed]}

It is used in line breeding, where animals carry a common ancestor in their pedigrees and are bred together, to restore vigor or size and fertility to a breeding line. It is a form of "inbreeding" which is the production of offspring by parents more closely related than the average.^[1]

Outcrossing is now the norm of most purposeful animal breeding, contrary to what is commonly believed.^[2]^[3]^[4]^[5] The outcrossing breeder intends to remove the traits by using "new blood". With dominant traits, one can still see the expression of the traits and can remove those traits whether one outcrosses, line breeds or inbreds. With recessive traits, outcrossing allows for the recessive traits to migrate across a population. The outcrossing breeder then may have individuals that have many deleterious genes that may be expressed by subsequent inbreeding. There is now a gamut of deleterious genes within each individual in many dog breeds.^[6]

Increasing the variation of genes or alleles within the gene pool may protect against extinction by stressors from the environment. For example, in this context, a recent veterinary medicine study tried to determine the genetic diversity within cat breeds.^[7]

Outcrossing is believed to be the "norm" in the wild.^[6] Outcrossing in plants is usually enforced by self-incompatibility.

Breeders inbreed within their genetic pool, attempting to maintain desirable traits and to cull those traits that are undesirable. When undesirable traits begin to appear, mates are selected to determine if a trait is recessive or dominant. Removal of the trait is accomplished by breeding two individuals known not to carry it.^[8]

Gregor Mendel used outcrossing in his experiments with flowers. He then used the resulting offspring to chart inheritance patterns, using the crossing of siblings, and backcrossing to parents to determine how inheritance functioned.^[9]

References

^ Guy Fawkes Horses Retrieved on 2009-8-1^{[dead link]}
^ Cat Fanciers: American Curl: Cat Breed FAQ
^ The Balinese Cat in the UK
^ Inbreeding: A Personal Point of View
^ Outcrossing in hunting dogs
^ ^a ^b Price
^ http://www.vgl.ucdavis.edu/lyons/index.php
^ [1]
^ Mendel's Paper (English - Annotated)

English Journal

Heterosis and outbreeding depression in crosses between natural populations of Arabidopsis thaliana.

Oakley CG1, Ågren J2, Schemske DW3.
Heredity.Heredity (Edinb).2015 Jul;115(1):73-82. doi: 10.1038/hdy.2015.18. Epub 2015 Mar 18.
Understanding the causes and architecture of genetic differentiation between natural populations is of central importance in evolutionary biology. Crosses between natural populations can result in heterosis if recessive or nearly recessive deleterious mutations have become fixed within populations b
PMID 26059971

Mating with an allopatric male triggers immune response and decreases longevity of ant queens.

Schrempf A1, von Wyschetzki K1, Klein A1, Schrader L1, Oettler J1, Heinze J1.
Molecular ecology.Mol Ecol.2015 Jul;24(14):3618-27. doi: 10.1111/mec.13267. Epub 2015 Jul 2.
In species with lifelong pair bonding, the reproductive interests of the mating partners are aligned, and males and females are expected to jointly maximize their reproductive success. Mating increases both longevity and fecundity of female reproductives (queens) of the ant Cardiocondyla obscurior,
PMID 26059759

On some genetic consequences of social structure, mating systems, dispersal, and sampling.

Parreira BR1, Chikhi L2.
Proceedings of the National Academy of Sciences of the United States of America.Proc Natl Acad Sci U S A.2015 Jun 30;112(26):E3318-26. doi: 10.1073/pnas.1414463112. Epub 2015 Jun 16.
Many species are spatially and socially organized, with complex social organizations and dispersal patterns that are increasingly documented. Social species typically consist of small age-structured units, where a limited number of individuals monopolize reproduction and exhibit complex mating strat
PMID 26080393

Japanese Journal

Genetic Diversity and Structure of Euryale ferox Salisb. (Nymphaeaceae) in Japan

APG : Acta phytotaxonomica et geobotanica 66(1), 1-9, 2015-02-27
NAID 110009922431

Breeding System and Seed Production in Pin-monomorphic Populations of a Distylous Perennial, Ophiorrhiza japonica (Rubiaceae) on Iriomote Island, Japan

APG : Acta phytotaxonomica et geobotanica 65(1), 43-48, 2014-02-28
NAID 110009816923