This article is about the technique used in animal and plant breeding. For naturally occurring outcrossing, see Allogamy.
Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity.
Outcrossing can be a useful technique in animal breeding. 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 inbreeds. With recessive traits, outcrossing allows for the recessive traits to migrate across a population. Many traits are Mendelian and therefore exhibit a more complicated intermediate phenotype. 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.[1]
Increasing the variation of genes or alleles within the gene pool may protect against extinction by stressors from the environment among inbred animal populations. For example, in this context, a recent veterinary medicine study tried to determine the genetic diversity within cat breeds.[2]
A degree of outcrossing to avoid mating between very close relatives is believed to happen in the wild.[1]
Outcrossing in fungi involves syngamy between haploid cells produced by separate diploid individuals.[3]
Life-history traits are said to increase the probability of outcrossing in fungi such as long-distance dispersal and persistence of the haploid stage. Some studies even show that fungi favor outcrossing in comparison to other mating types. In a study performed with the commercial button mushroom, Agaricus bisporus, outcrossed populations of the fungi showed higher fitness than inbred ones in several fitness components.[4]
General practiceedit
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.[5]
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.[6]
Darwin's perspectiveedit
Charles Darwin, in his book The Effects of Cross and Self-Fertilization in the Vegetable Kingdom,.[7]: 462 stated regarding outcrossing that "the offspring from the union of two distinct individuals, especially if their progenitors have been subjected to very different conditions, have an immense advantage in height, weight, constitutional vigor and fertility over the self-fertilizing offspring from either one of the same parents". He thought that this observation was amply sufficient to account for outcrossing sexual reproduction. The disadvantages of self-fertilized offspring (inbreeding depression) are now thought to be largely due to the homozygous expression of deleterious recessive mutations;[8] and the fitness advantages of some outcrossed offspring are thought to be largely due to the heterozygous masking of such deleterious mutations except when such mutations lead to outbreeding depression.
^ abSharp, C.A. (26 February 1999). . Canine-Genetics.com. Double Helix Network News Vol. VII, No. 1 (Winter 1999). Archived from the original on 26 January 2012.
^. UC Davis Veterinary Genetics Laboratory. Archived from the original on 2009-03-12.
^Billiard, S.; López-Villavicencio, M.; Hood, M. E.; Giraud, T. (2012). "Sex, outcrossing and mating types: unsolved questions in fungi and beyond". Journal of Evolutionary Biology. 25 (6): 1020–1038. doi:10.1111/j.1420-9101.2012.02495.x. PMID 22515640. S2CID 25007801.
^Xu, J. (1995). "Analysis of inbreeding depression in Agaricus bisporus". Genetics. 141 (1): 137–145. doi:10.1093/genetics/141.1.137. PMC1206712. PMID 8536962.
^David M. Hillis. "Inbreeding, Linebreeding, and Outcrossing in Texas Longhorns". University of Texas at Austin.
^"Mendel's Paper (English - Annotated)". www.mendelweb.org.
^"Darwin, C. R. 1876. The effects of cross and self fertilisation in the vegetable kingdom. London: John Murray". darwin-online.org.uk.
^Bernstein H, Hopf FA, Michod RE (1987). "The molecular basis of the evolution of sex". Adv. Genet. Advances in Genetics. 24: 323–70. doi:10.1016/s0065-2660(08)60012-7. ISBN9780120176243. PMID 3324702.
February 15, 2024
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This article is about the technique used in animal and plant breeding For naturally occurring outcrossing see Allogamy Out crossing or out breeding is the technique of crossing between different breeds This is the practice of introducing distantly related genetic material into a breeding line thereby increasing genetic diversity Labradoodles a crossbreed between a Poodle and a Labrador Retriever Contents 1 Outcrossing in animals 2 Outcrossing in plants and fungi 3 General practice 4 Darwin s perspective 5 See also 6 ReferencesOutcrossing in animals editOutcrossing can be a useful technique in animal breeding 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 inbreeds With recessive traits outcrossing allows for the recessive traits to migrate across a population Many traits are Mendelian and therefore exhibit a more complicated intermediate phenotype 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 1 Increasing the variation of genes or alleles within the gene pool may protect against extinction by stressors from the environment among inbred animal populations For example in this context a recent veterinary medicine study tried to determine the genetic diversity within cat breeds 2 A degree of outcrossing to avoid mating between very close relatives is believed to happen in the wild 1 Outcrossing in plants and fungi editOutcrossing in plants is usually enforced by self incompatibility Outcrossing in fungi involves syngamy between haploid cells produced by separate diploid individuals 3 Life history traits are said to increase the probability of outcrossing in fungi such as long distance dispersal and persistence of the haploid stage Some studies even show that fungi favor outcrossing in comparison to other mating types In a study performed with the commercial button mushroom Agaricus bisporus outcrossed populations of the fungi showed higher fitness than inbred ones in several fitness components 4 General practice editBreeders 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 5 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 6 Darwin s perspective editCharles Darwin in his book The Effects of Cross and Self Fertilization in the Vegetable Kingdom 7 462 stated regarding outcrossing that the offspring from the union of two distinct individuals especially if their progenitors have been subjected to very different conditions have an immense advantage in height weight constitutional vigor and fertility over the self fertilizing offspring from either one of the same parents He thought that this observation was amply sufficient to account for outcrossing sexual reproduction The disadvantages of self fertilized offspring inbreeding depression are now thought to be largely due to the homozygous expression of deleterious recessive mutations 8 and the fitness advantages of some outcrossed offspring are thought to be largely due to the heterozygous masking of such deleterious mutations except when such mutations lead to outbreeding depression See also editConsanguinity Heterosis Outbreeding depressionReferences edit a b Sharp C A 26 February 1999 The Downside of Inbreeding It s Time For a New Approach Canine Genetics com Double Helix Network News Vol VII No 1 Winter 1999 Archived from the original on 26 January 2012 Feline Genetics UC Davis Veterinary Genetics Laboratory Archived from the original on 2009 03 12 Billiard S Lopez Villavicencio M Hood M E Giraud T 2012 Sex outcrossing and mating types unsolved questions in fungi and beyond Journal of Evolutionary Biology 25 6 1020 1038 doi 10 1111 j 1420 9101 2012 02495 x PMID 22515640 S2CID 25007801 Xu J 1995 Analysis of inbreeding depression in Agaricus bisporus Genetics 141 1 137 145 doi 10 1093 genetics 141 1 137 PMC 1206712 PMID 8536962 David M Hillis Inbreeding Linebreeding and Outcrossing in Texas Longhorns University of Texas at Austin Mendel s Paper English Annotated www mendelweb org Darwin C R 1876 The effects of cross and self fertilisation in the vegetable kingdom London John Murray darwin online org uk Bernstein H Hopf FA Michod RE 1987 The molecular basis of the evolution of sex Adv Genet Advances in Genetics 24 323 70 doi 10 1016 s0065 2660 08 60012 7 ISBN 9780120176243 PMID 3324702 Retrieved from https en wikipedia org w index php title Outcrossing amp oldid 1197714595, wikipedia, wiki, book, books, library,
