Inbreeding depression

Inbreeding depression

Inbreeding depression is reduced fitness in a given population as a result of breeding of related individuals. Breeding between closely related individuals, called inbreeding, results in more recessive deleterious traits manifesting themselves. The more closely related the breeding pair is, the more homozygous deleterious genes the offspring may have, resulting in very unfit individuals. Another mechanism responsible is overdominance of heterozygous alleles leading to a reduction in the fitness of a population with many homozygous genotypes, even if they are not deleterious. Currently it is not known which of the two mechanisms is more important. In general, populations with more genetic variation do not suffer from inbreeding depression. Inbreeding depression is often the result of a population bottleneck. Inbreeding depression seems to be present in most groups of organisms, but is perhaps most important in hermaphroditic species, most prominently in plants. The majority of plants are hermaphroditic and thus are capable of the most severe degree of inbreeding.

Inbreeding depression and natural selection

Natural selection cannot effectively remove all deleterious recessive genes from a population for several reasons. First, deleterious genes arise constantly through mutation within a population. Second, in a population where inbreeding occurs frequently, most offspring will have some deleterious traits, so few will be more fit for survival than the others. It should be noted, though, that different deleterious traits are extremely unlikely to equally affect reproduction. An especially disadvantageous recessive trait expressed in a homozygous recessive individual is likely to eliminate itself, naturally limiting the expression of its phenotype. Third, recessive deleterious alleles will be "masked" by heterozygosity, and so heterozygotes will not be selected against (assuming dominance).

Managing inbreeding depression

Introducing new genes from a different population can reverse inbreeding depression. Different populations have different deleterious traits, and therefore will not result in homozygosity in most loci in the offspring. This is known as outbreeding enhancement, practiced by conservation managers and zoo captive breeders to prevent homozygosity. However, intermixing two different populations may give rise to unfit polygenic traits in outbreeding depression

In humans

Although severe inbreeding depression in humans seems to be highly uncommon and not widely known, there have been several cases of apparent forms of inbreeding depression in human populations. As with animals, this phenomenon tends to occur in isolated, rural populations that are cut off to some degree from other areas of civilization. Some notable examples include:

*The Vadoma tribe of western Zimbabwe, many of whom carry the trait of having only two toes due to a small gene pool.

*The Ulas family of southern Turkey have several members who walk on all fours, due to mental retardation caused by inbreeding.

Example taxa subject to inbreeding depression

* "Amaranthus brownii"
*Chillingham Cattle - a cattle breed
*"Piperia yadonii"Verify source|date=August 2007

Example taxa not subject to significant inbreeding depression

despite extremely low effective population sizes
* Chatham Islands Robin
* Laysan Duck (data equivocal; severe population fluctuations probably natural)
* Mauritius Kestrel
* Nihoa Carnation
* Thai Ridgeback, a dog breed
* ToromiroVerify source|date=April 2007

ee also

*Inbreeding
*Hybrid vigour
*Minimum viable population
*Population genetics
*Backward evolution
*Vadoma

References

* [http://www.nwfsc.noaa.gov/publications/techmemos/tm30/lynch.html Genetic Effects of Straying of Non-Native Hatchery Fish into Natural Populations]


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Look at other dictionaries:

  • inbreeding depression — inbreeding depression. См. инцухт депрессия. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • inbreeding depression — įvaisinė depresija statusas T sritis augalininkystė apibrėžtis Sumažėjęs palikuonių gyvybingumas, augimas, produktyvumas dėl priverstinės savidulkos. atitikmenys: angl. inbreeding depression rus. инбредная депрессия ryšiai: sinonimas –… …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • inbreeding depression — A loss of fitness due to severe inbreeding …   Dictionary of invertebrate zoology

  • inbreeding depression — /ɪnbridɪŋ dəˈprɛʃən/ (say inbreeding duh preshuhn) noun Biology the lowered fitness or vigour of inbred individuals compared with their non inbred counterparts …  

  • inbreeding depression — The reduction in vigour over generations of inbreeding. This affects species which are normally outbreeding and highly heterozygous. See: hybrid vigour …   Glossary of Biotechnology

  • inbreeding depression — loss of vigour associated with repeated crosses between closely related individuals …   Dictionary of ichthyology

  • Inbreeding — is breeding between close relatives, whether plant or animal. If practiced repeatedly, it leads to an increase in homozygosity of a population. A higher frequency of recessive, deleterious traits in homozygous form in a population can, over time …   Wikipedia

  • Dépression endogamique — La dépression endogamique, ou dépression de consanguinité, désigne la réduction de la valeur sélective d une population donnée liée à la reproduction entre individus apparentés. La reproduction entre individus étroitement apparentés, ou… …   Wikipédia en Français

  • Dépression hybride — En biologie de l évolution, on parle de dépression hybride quand la descendance d un croisement entre individus de population différente ont une valeur sélective (ou fitness en anglais) moins importante que les deux parents. La distance génétique …   Wikipédia en Français

  • Outbreeding depression — A concept in selective breeding and zoology, outbreeding depression refers to cases when offspring from crosses between individuals from different populations have lower fitness than progeny from crosses between individuals from the same… …   Wikipedia

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