In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a small number of individuals from a larger population. It was first outlined entirely by Ernst Mayr in 1942, using the theoretical works available to people like Sewall Wright. As a result of the loss of genetic variation, the new population may differ typically, both genotypically and phenotically, from the parent population from which it originated. In extreme cases, the founder's effect is considered to lead to the speciation and subsequent evolution of the new species.
In the figure shown, the native population has nearly equal numbers of blue and red individuals. Three smaller founding populations indicate that one or another color may predominate (founder effect), due to random sampling of the original population. Population congestion can also cause founder effects, although not entirely new populations.
The founder effect occurs when a small group of migrants who do not represent the genetic population from which they came to build in a new area. In addition to the founder's effect, the new population is often a very small population, thus indicating increased sensitivity to genetic drift, inbreeding increase, and relatively low genetic variation.
Video Founder effect
The founder's mutation
In genetics, founders of mutations are mutations that appear in the DNA of one or more individuals who are the founders of different populations. The founder's movements begin with changes that occur in DNA and can be passed on to other generations. Mutations can occur in any organism that becomes the founder of a mutated lineage that can be as simple as a more complex virus, goat, or human being.
The founder's mutation comes from a long stretch of DNA on a single chromosome; indeed, the original haplotype is the entire chromosome. As the development of generations, the proportion of haplotypes common to all carriers of mutations is shortened (due to genetic recombination). This shortening allows scientists to roughly estimate the age of the mutation.
Maps Founder effect
General
The founding effect is a special case of genetic shift, occurring when small groups within the population are disconnected from the native population and form new ones. New colonies may have fewer genetic variations than indigenous populations, and through random sampling of alleles during subsequent generation reproduction, continues toward fixation. The consequences of this inbreeding make the colony more vulnerable to extinction.
When the newly formed colony is small, its founders can greatly influence the genetic makeup of the population far into the future. In humans, who have a slow reproductive rate, the population will remain small for generations, effectively reinforcing the effect of shifting generation after generation until the population reaches a certain size. The present allele but relatively rare in the native population can move to one of two extremes. The most common is that the allele disappears altogether, but the other possibility is that the allele survives and in several generations has become much more widespread throughout the population. The new colony may experience an increase in the frequency of the recessive allele, as well, and as a result, a homozygous increase in the amount of certain recessive properties.
Variations in gene frequencies between indigenous populations and colonies can also trigger both groups to deviate significantly over many generations. As the variance, or genetic distance, increases, the two separate populations can be distinctively different, both genetically and phenotypically, although not only genetic aberrations, but also natural selection, gene flow and mutations all contribute to this distinction. The potential for a relatively rapid change in the frequency of these colony genes led most scientists to consider the founder effect (and with extension, genetic drift) a significant driving force in the evolution of new species. Sewall Wright was the first to attach this significance to random deviations and a small, newly isolated population with its shifting theories of shifting balance. Following behind Wright, Ernst Mayr created many persuasive models to show that the decrease in genetic variation and small population size that accompany the founding effect is essential for new species to be developed. However, much less support for this view is shown today, because the hypothesis has been tested repeatedly through experimental research, and the results have been vague. Speciation by genetic shift is a specific case of peripatric speciation which in itself occurs in rare cases. This occurs when random changes in the population's genetic frequency support the survival of some organisms from species with rare genes that cause reproductive mutations. These surviving organisms then multiply among themselves for long periods of time to create new species whose reproductive systems or behavior no longer correspond to the original population.
Series founding effect
Serial setting effects occur when populations migrate over long distances. Such long-distance migration usually involves a relatively rapid movement followed by a period of settlement. The population in each migration only carries a subset of the genetic diversity brought about from previous migrations. As a result, genetic differentiation tends to increase with geographic distance as described by the "isolation by distance" model. Human migration from Africa is characterized by the serial founder effect. Africa has the highest genetic diversity on any continent, consistent with modern humans from Africa. After the initial migration from Africa, the Indian subcontinent is the first major precipitation point for modern humans. As a result, India has the second highest genetic diversity in the world. In general, genetic diversity of the Indian subcontinent is part of Africa, and genetic diversity outside Africa is part of India.
In the archipelagic ecology
The founder of the population is very important to study the island's biogeography and island ecology. A natural "blank slate" is not easy to find, but a series of classical studies on the effects of the population of its founders were made after the eruption of Krakatoa in 1883, which erased all life on the island. Other sustainable studies have followed the biocolonization of Surtsey, Iceland, a new volcanic island that erupted offshore between 1963 and 1967. Previous events, the Toba eruption in Sumatra about 73,000 years ago, covered parts of India by 3-6 m (10 -20Ã, ft) of ash, and should be coated with the Nicobar Islands and Andaman Islands, much closer to the cones of ash fragments, with layers strangling life, forcing to restart their biodiversity.
However, not all founder effect studies begin after natural disasters; some scientists study the recovery of a species that became extinct locally. Hajj and others, and Hundertmark & ​​â € <â € < Van Daele, studying the current population status of past founder effects in the Corsican red deer and Alaskan deer, respectively. Corsican red deer are still listed as endangered species, decades after a severe congestion. They inhabit the island of Tyrrhenian and the surrounding landmass at present, and before congestion, but Hajji and others want to know how the deer initially reached the islands, and which of the populations or species of parents they came from. Through molecular analysis, they were able to determine possible lineages, with red deer from the Corsica and Sardinian islands most closely related to each other. These results are promising, as the Corsica island is re-populated with red deer from the island of Sardinia after the original Corsican red deer population becomes extinct, and the deer that now inhabit the island of Corsica deviate from the people who inhabit Sardinia.
Kolbe and others set up a pair of lizards examined genetically and morphologically on seven small islands to observe each new population growth and adaptation to their new surroundings. In particular, they see effects on the length of the extremities and the width of the perch, both the phenotypic ranges that vary widely in the parental population. Unfortunately, immigration does occur, but the effects of the founder and adaptive differentiation, which may eventually lead to peripatric speciation, are statistically and biologically significant between island populations after several years. The authors also point out that although adaptive differentiation is significant, the differences between island populations most reflect differences between founders and their genetic diversity that has been passed down from generation to generation.
In the human population
Due to various migrations throughout human history, the effects of the founders are rather common among humans in different times and places. Canada Canada France is a classic example of its population of founders. During the 150 years of French colonization, between 1608 and 1760, an estimated 8,500 pioneers were married and left at least one offspring in the region. After the colonial takeover by the British Empire in 1760, immigration from France effectively ceased, but the descendants of French settlers continued to increase in numbers mainly due to the high fertility rate. Marriage occurs mainly with Indians and deported migrants from the British Isles. Since the 20th century, immigration in Quebec and the mixing of French Canadians involve people from all over the world. While Canadian French Canada today may be part of another ancestor, the genetic contribution of the original French founder was of prime importance, explaining about 90% of regional gene pools, while Acadians (descendants of other French settlers in eastern Canada) explained 4% 2% and Native Americans and other groups contribute less.
In humans, the effects of the founder can arise from cultural isolation, and inevitably, endogamy. For example, the Amish population in the United States shows the founding effect because they have grown from very few founders, have not recruited new arrivals, and tend to marry in the community. Although still rare, phenomena such as polydactyly (extra fingers and toes, symptoms of conditions such as Weyers acrodental dysostosis or Ellis-van Creveld syndrome) are more common in Amish communities than in the general American population. Maple syrup disease affects about one in 180,000 infants in the general population. Due in part to the effects of the founders, however, this disease has a much higher prevalence in children than Amish, Mennonite, and Jewish descent. Similarly, the high frequency of fumarase deficiency is among the 10,000 members of the Fundamentalist Church of Jesus Christ of Latter-day Saints, a community that practices both endogamy and polygyny, where it is estimated that 75 to 80% of the community are bloody families of only two males - founders John Y. Barlow and Joseph Smith Jessop.
Around the year 1814, a small group of British colonists established settlements in Tristan da Cunha, a small island group in the Atlantic Ocean, halfway between Africa and South America. One early colony apparently carried a rare alleles, recessive for retinitis pigmentosa, a progressive form of blindness that affects individual homozygotes. By the end of 1961, most of the genes in Tristan's gene pool were still from the original 15 ancestors; as a result of inbreeding, of 232 people tested in 1961, four had retinitis pigmentosa. This is a prevalence of 1 in 58, compared with worldwide prevalence of about 1 in 4,000.
The extremely high birth rates of twins in CÃÆ'n nons GodÃÆ'³i can be explained by the founding effect.
In language
The founding effect in the language underscores the impact of the founding population on the nature of the language arising from reclamation or creolization. For example, according to the linguist Ghil'ad Zuckermann, "Yiddish is a major contributor to the Hebrew language of Israel because of the mother tongue of most of the first revivalists and pioneers in Eretz Yisrael in the crucial period of the beginning of the Hebrew of Israel." According to Zuckermann, although Hebrew revivalists (ie founders of the Israel language) want to speak Hebrew, with Semitic grammar and pronunciation, they can not avoid the Ashkenazi mindset originating from their European background. He argues that the revivalists' attempt to reject their European roots, abolish diasporism, and avoid hybridity as reflected in Yiddish, failed. "If the revivalists were Arabic-speaking Jews (eg from Morocco), the Hebrew Israel would be a completely different language - genetically and typologically, much more Semitic." The "Founding Principles" of such linguistics lead Zuckermann to assert that Israel (the language used in Israel today) is a Semito-European hybrid not just Hebrew.
See also
- Cousin's wedding
- Genetic Inhibition
- Inbreeding depression
- Mitochondrial Night
- Neolithic Founder Plant
- The popular sire effect
- Small population size
References
Further reading
- Mayr, Ernst (1954). "Environmental change and genetic evolution". At Julian Huxley. Evolution as Process . London: George Allen & amp; Unwin. OCLCÃ, 974739.
- Mayr, Ernst (1963). Animal Species and Evolution . Cambridge: Belknap Press from Harvard University Press. ISBN 0-674-03750-2.
External links
- Founder Effects
Source of the article : Wikipedia
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