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Topic: Founder population

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Krakatoa

	Population bottleneck - Wikipedia, the free encyclopedia
		A population bottleneck (or genetic bottleneck) is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more, often by several orders of magnitude.
		Population bottlenecks increase genetic drift, as the rate of drift is inversely proportional to the population size.
		A classic example of a population bottleneck is that of the northern elephant seals, whose population fell to about 30 in the 1890's although it now numbers in the tens of thousands.
	en.wikipedia.org /wiki/Population_bottleneck (542 words)

	Founder population - Wikipedia, the free encyclopedia
		The concept of a founder population is usually seen in a context of subsequent population growth.
		Such populations that have recently arisen from small founder populations will exhibit reduced genetic variation due to the population bottleneck.
		A recent study (Hey 2005) concluded that of the people migrating across the Bering land bridge at the close of the ice age, only 70 left their genetic print in modern descendents, a minute effective founder population— which is easily misread as though implying that only 70 people crossed to North America.
	en.wikipedia.org /wiki/Founder_population (492 words)

	founder population (Site not responding. Last check: 2007-11-02)
		When a species invades a new area, especially an island, the original, small population is called a founder population.
		The concept of a founder population is usually used in a context of subsequent population growth, and populations that have recently arisen from small founder populations will exhibit reduced variation due to the genetic drift implied by such a population bottleneck.
		Classic series of studies on founder population effects were done following the catastrophic eruption in 1883 of Krakatau, ('Krakatoa'), which erased all life on the island remnant.
	www.yourencyclopedia.net /founder_population.html (190 words)

	Purebred Dog Breeds into the Twenty-First Century (Site not responding. Last check: 2007-11-02)
		Population geneticists insist that limited populations under strong artificial selection, subjected to high levels of incest simply cannot maintain genetic viability and vigor in the long term without the periodic introduction of new and unrelated genetic material.
		It is, of course, caused by the presence of lethal, sublethal and subvital alleles.
		Population geneticists and evolutionary biologists now realise that typological concepts are useless in a natural world in which populations may best be described genetically not as individuals conforming to a type but as arrays of genetic variability.
	www.geocities.com /tycarreg/03b/purebred-dog-breeds.htm (11764 words)

	Phenotypic characterization and genealogical tracing in an Afrikaner schizophrenia database.
		Founder populations hold tremendous promise for mapping genes for complex traits, as they offer less genetic and environmental heterogeneity and greater potential for genealogical research.
		The Afrikaner population meets several criteria that make it an ideal population for mapping complex traits, including founding by a small number of initial founders that likely allowed for a relatively restricted set of mutations and a large current population size that allows identification of a sufficient number of cases.
		Based on the results presented here, the history and current size of the population, as well as our previous analysis addressing the extent of background linkage disequilibrium (LD) in the Afrikaners, we conclude that the Afrikaner population is likely an appropriate founder population to map genes for schizophrenia using both linkage and LD approaches.
	www.sph.umich.edu /csg/abecasis/publications/14681908.html (272 words)

	Founder effect - EvoWiki (Site not responding. Last check: 2007-11-02)
		The founder effect is a form of genetic bottleneck occuring where new populations are established by a small number of individuals, or by a group of individuals whose genetic variation is not representative of the parent population.
		The founder effect is a cause of genetic drift because the daughter population contains only a sample of the alleles from the parent population.
		The founder effect can be seen in many human populations, as Africans have far more genetic variation than the inhabitants of any other continent, whose occupants are descended from migrants from Africa.
	wiki.cotch.net /index.php/Founder_effect (244 words)

	MCDB 2150 -- Lecture 40
		The second is the so-called founder effect, which results from the chance inclusion of certain alleles in the small founder population, as described below..
		Founder effect: One of the potential consequences of a bottleneck is a high frequency of recessive genetic diseases in the population resulting from one of the founders happening to be a carrier of a relatively rare disease whose heterozygote frequency is much higher than its homozygous frequency.
		The founder effect is based on the fact that a small sample may differ substantially in composition from the larger population it is drawn from, purely by random "sampling errors".
	www.colorado.edu /MCDB/MCDB2150Fall/notes/L40.html (2212 words)

	Evolution - A-Z - Founder effect
		The founder effect is a particular example of the influence of random sampling.
		Isolated populations often have exceptionally high frequencies of otherwise rare alleles, and the most likely explanation is that the founding population had a disproportionate number of those rare alleles.
		Figure: the chance that a founder population will be homozygous depends on the number of founders and the gene frequencies.
	www.blackwellpublishing.com /ridley/a-z/Founder_effect.asp (342 words)

	BIOdotEDU
		If a small number of individuals are separated from the original population, and the conditions are right, the smaller group can go on to form a new breeding population of their own, and thus start (or "found") a whole new species.
		New populations that arise from the founder effect clearly have different evolutionary potentials from the original populations.
		Founder populations are usually very small; therefore, change can be quite rapid and these populations can accumulate new adaptations much faster than large populations.
	www.brooklyn.cuny.edu /bc/ahp/LAD/C21/C21_Founder.html (360 words)

	Zoology 510, Chapter 6 notes
		The founder effect is not the same as genetic drift, since drift is cumulative change over many generations.
		Population size may vary from generation to generation, with significant "bottlenecks" of low population size.
		Effective population size significantly affects the expectations of drift, founder effect, and march to homozygosity.
	www.science.siu.edu /zoology/king/510/mr06.htm (2316 words)

	Allopatric speciation - EvoWiki (Site not responding. Last check: 2007-11-02)
		The isolation of a population of meiotic organisms inhibits the flow of genes between adjacent populations, and it is this flow of genes which maintains the homogeneity (relatively speaking) of contiguous populations.
		The accumulation of genotypic differences and subsequent alteration in the phenotype of the incipient species population produces isolating mechanisms which inhibit the reproductive potential of the isolated population and its conspecific parent population.
		The restricted genotype of this founder population is central to the restructuring of the genotype within this founder population (see Founder effect), and thus fuels the establishment of isolating mechanisms whereby the new population, will form a neospecies at some future date.
	www.evowiki.org /index.php/Allopatric_speciation (347 words)

	Encyclopedia: Founder population
		Genetic drift is a mechanism of evolution that acts in concert with natural selection to change the characteristics of species over time.
		After twelve to sixteen generations, with an eighty-fold growth but minimal gene dilution from intermarriage, Quebec has what geneticists call optimal linkage disequilibrium (genetic sharing)[1].
		Beginning in 1963, a terrorist group that became known as the Front de libÃ©ration du QuÃ©bec (FLQ) launched a decade of bombings, robberies and attacks on government offices and at least two murders by FLQ gunfire and three violent deaths by bombings.
	www.nationmaster.com /encyclopedia/Founder-population (918 words)

	Purebred Dog Breeds into the 21st Century (Site not responding. Last check: 2007-11-02)
		Population geneticists insist that limited populations under strong artificial selection, subjected to high levels of incest breeding -- such as our own CKC purebreds -- simply cannot maintain genetic viability and vigour in the long term without the periodic introduction of new and unrelated genetic material.
		Since in limited, genetically isolated populations such as CKC breeds a certain amount of genetic diversity is lost with each reproductive event, through the action of genetic drift, inbreeding and artificial selection, the number of generations from the founder event becomes an issue.
		Then it is possible that bad alleles, uncommon in the canine population as a whole, may achieve a much higher frequency of occurrence owing to their presence in a small founder population -- especially since the foundation stock of a newly-recognised breed will already be considerably inbred from the breed development process.
	seppalasleddogs.com /documents/pbdb21c.htm (15662 words)

	Founder population (Site not responding. Last check: 2007-11-02)
		The concept of a founderpopulation is usually used in a context of subsequent population growth, and populations that have recently arisen from smallfounder populations will exhibit reduced variation due to the geneticdrift implied by such a population bottleneck.
		Classic series ofstudies on founder population effects were done following the catastrophic eruption in 1883 of Krakatau, (' Krakatoa '), which erased all life on the island remnant.
		Another ongoing study has beenfollowing the biocolonization of Surtsey, Iceland, a new volcanicisland that erupted offshore between 1963 and 1967.
	www.therfcc.org /founder-population-120407.html (140 words)

	[No title]
		Founder effect depends on allele frequencies in source population and number of founders (Nf) 1.
		Collared lizards populations are currently limited to scattered, small exposed rocky outcrops (glades) that are islands in the forested habitat.
		Populations on glades are small, therefore they should show evidence of drift [fig.
	users.tamuk.edu /kfjab02/Biology/EVOLUTION/b3301ppt/BIOL3301ch06.doc (1624 words)

	Linkage disequilibrium mapping in isolated populations: The example of Finland revisited -- de la Chapelle and Wright ... (Site not responding. Last check: 2007-11-02)
		a founder effect and compounded by subsequent genetic drift (13).
		The distributions are very similar, showing that recent moves from the eastern and north-central parts of the country to the south and west that would significantly distort the distribution have not occurred.
		of the population of disease chromosomes typically is observed
	www.pnas.org /cgi/content/full/95/21/12416 (6142 words)

	News in Science - Romany Gypsies came out of India - 06/09/2004
		The researchers were first alerted to the idea that the Romany may be descended from a small founder population when they discovered that certain genetic mutations in the population were shared in people who were not directly related.
		The aim was to try and estimate when the original founder population arose and when it split off into different groups of Romany.
		"There are quite a few examples where a population adopts a language but this does not necessarily mean its biological roots belong to the same place as the larger population that speaks this language," she said.
	www.abc.net.au /science/news/stories/s1191889.htm (713 words)

	HUGO HGM2003 - Presentation 7 - Genetics of Complex Traits in a Founder Population of Canada (Site not responding. Last check: 2007-11-02)
		The genetic causes of complex genetic diseases such as asthma and coronary heart disease are being studied in the Saguenay-Lac St. Jean region of Quebec.
		Most of the 280,000 individuals of this 12-generation-old population are descendants of early settlers who came to New France in the 17th century.
		The linkage and linkage disequilibrium studies in progress for both asthma and early-onset coronary heart disease follow a hierarchical strategy, where loci identified in genome scan studies are further analyzed using high-density SNP screens.
	hgm2003.hgu.mrc.ac.uk /Abstracts/Publish/Plenaries/Plenary03/hgm07.html (306 words)

	Galileo Genomics Unveils an 80,700 SNP Quebec Linkage Disequilibrium Map for use in Genome-Wide Association Studies (Site not responding. Last check: 2007-11-02)
		The QLDM is based on measurement of LD using a unique multiple marker algorithm and data from a study of 1,500 members of the QFP using 248,000 SNPs and a total of 372 million genotypes, genotypes generated in collaboration with Perlegen Sciences and using that company's advanced knowledge of the human genome.
		Galileo is applying the QLDM to 20 gene discovery programs in common diseases for which it has been collecting samples from the Quebec Founder Population for the past 3 years.
		In recognition of the contribution to Galileo's research made by the Quebec Founder Population, the company has committed to donate three per cent of its net profits to a trust fund for the benefit of Quebecers.
	www.forrelease.com /D20041026/1132073.html (680 words)

	MCDB 2150 -- Lecture 38
		In addition, other factors, such as heterozygote advantage, may increase the fraction of the alleles retained in the population, even under conditions where the basis for the advantage is not fully understood.
		There is also a risk that deleterious genes may become fixed in the population due to genetic drift during the bottleneck period (pages 598-602); see also discussion of inbreeding depression and hybrid vigor on pages 615-617).
		Thus, in addition to inbreeding and founder effects, a population that goes through a bottleneck and stays small for a while may become more homozygous through genetic drift (see pages 598-602).
	www.colorado.edu /MCDB/MCDB2150Fall/notes99/99L38.html (2515 words)

	Genetic Models in Applied Physiology: Selected Contribution: Variation and heritability for the adaptational response ...
		The pretraining estimate of capacity for the founder rats was
		Figure 2 displays the founder and generation 1 values for response to training in the form of frequency histograms.
		Slopes were <1 for both founder and generation 1 low-line rats, indicating that low intrinsic capacity (pretraining) was associated with a greater response to training.
	jap.physiology.org /cgi/content/full/94/4/1674 (4585 words)

	Zoology 304, Evolution
		We often introduce population genetics using models, such as the Hardy-Weinberg equilibrium, which assumes large populations in which drift is unimportant.
		In a diploid population of N individuals, there are 2N genes at a given locus.
		Any factor which decreases effective population size will decrease the expected heterozygosity (or, equivalently, increase the homozygosity, or inbreeding) of the actual population.
	www.science.siu.edu /zoology/king/304/drift.htm (1471 words)

	Genetic Health for Dogs
		Population geneticists insist that limited populations under strong artificial selection, subjected to high levels of incest breeding - such as our own CKC purebreds -- simply cannot maintain genetic viability and vigor in the long term without the periodic introduction of new and unrelated genetic material.
		Since in limited, genetically isolated populations such as CKC breeds a certain amount of genetic diversity is lost with each reproductive event through the action of genetic drift, inbreeding and artificial selection.
		Thus the recognition of a breed creates a founder event when the registry is opened; a limited number of breed foundation animals are selected, often from a population which has already undergone considerable inbreeding and selection.
	www.flockguard.org /breeding_genetics_bragg.htm (15570 words)

	NARSAD: Research Center: Project Summary for Michael A. Escamilla, M.D.
		This has typically been difficult, but the process can be enhanced if carried out in a “founder” population (populations where most current members come from a small group of ancestors).
		His work focuses on fine mapping and identification of susceptibility genes for Bipolar Disorder (BP) and SC in a founder population in the Central Valley of Costa Rica.
		Previous work in this population has provided the world with a location of a gene for BP and also led to the first identification of a gene that causes deafness.
	www.narsad.org /research/summaries/escamillamichaela-2002.html (196 words)

	Extended Intermarker Linkage Disequilibrium in the Afrikaners -- Hall et al. 12 (6): 956 -- Genome Research
		A common concern in using founder populations for mapping complex, multigenic traits is the relevance of the study's findings
		Eaves, I.A., Merriman, T.R., Barber, R.A., Nutland, S., Tuomilehto-Wolf, E., Tuomilehto, J., Cucca, F., and Todd, J.A. The genetically isolated populations of Finland and Sardinia may not be a panacea for linkage disequilibrium mapping of common disease genes.
		Goldman, A., Krause, A., Ramsay, M., and Jenkins, T. Founder effect and the prevalence of myotonic dystrophy in South Africans: Molecular studies.
	www.genome.org /cgi/content/full/12/6/956 (3157 words)

	SUSPS Verbal Congressional Testimony - SUSPS
		But, at least 60% of U.S. population growth in the 90's (twenty million) was from immigration and children born to immigrants.
		Given the crucial role of immigration in the current population boom we -- and 42 other environmental leaders listed in our written testimony (see attached) - realize that it must be addressed directly if we are to stabilize our numbers in the foreseeable future.
		Respected environmental organizations recognize that continued growth in U.S. population and our consumption is decimating the natural resources that this and future generations need to live healthy and satisfying lives.
	www.susps.org /info/congr_testimony_verbal_20010802.html (1285 words)

	Genetic Diseases in Ashkenazi Jews (Site not responding. Last check: 2007-11-02)
		The founder theory is of particular interest to geneticists because they theorize that even if just a few of these original founders had a mutation, the gene defect would then be passed on to their descendants for generations to come.
		A follow-up study in 1996 found two additional mutations (one in the BRCA 1 gene and one in another breast cancer gene called BRCA 2) to be at increased prevalence in the Ashkenazi Jewish population, bringing the overall risk for carrying one of these three mutations to 2.3 percent.
		As a result, the Tay-Sachs gene continued to be passed on in greater numbers within the Ashkenazi population, even though it threatened the lifespan of a small number of children who inherited two copies of the gene mutation, resulting in a fatal childhood illness.
	www.dnadirect.com /resource/genetics_101/GH_Ashkenazi.jsp (1098 words)

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