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PubMed2001

Founder effect in an island population of bighorn sheep.

The Tiburon Island population of desert bighorn sheep has increased in size from 20 founders in 1975 to approximately 650 in 1999. This population is now the only population being used as the source stock for transplantations throughout northern Mexico. To evaluate the genetic variation in this population, we examined 10 microsatellite loci and a major histocompatibility complex (MHC) locus. The genetic variation was significantly less than found in other populations of the same subspecies in Arizona. Using a model that takes into account the effects of genetic drift on genetic distance, most of the genetic distance observed between the Tiburon population and Arizona samples could be explained. Because of the low genetic variation found in the Tiburon population, it is suggested that the Tiburon population should be supplemented with additional unrelated animals or that the transplant populations should be supplemented with unrelated animals.

Animals↗
PubMed2003

Diverging patterns of mitochondrial and nuclear DNA diversity in subarctic black spruce: imprint of a founder effect associated with postglacial colonization.

High-latitude ecotonal populations at the species margins may exhibit altered patterns of genetic diversity, resulting from more or less recent founder events and from bottleneck effects in response to climate oscillations. Patterns of genetic diversity were investigated in nine populations of the conifer black spruce (Picea mariana [Mill.] BSP.) in northwestern Québec, Canada, using seed-dispersed mitochondrial (mt) DNA and nuclear (nc) DNA. mtDNA diversity (mitotypes) was assessed at three loci, and ncDNA diversity was estimated for nine expressed sequence tag polymorphism (ESTP) loci. Sampling included populations from the boreal forest and the southern and northern subzones of the subarctic forest-tundra, a fire-born ecotone. For ncDNA, populations from all three vegetation zones were highly diverse with little population differentiation (thetaN = 0.014); even the northernmost populations showed no loss of rare alleles. Patterns of mitotype diversity were strikingly different: within-population diversity and population differentiation were high for boreal forest populations [expected heterozygosity per locus (HE) = 0.58 and thetaM = 0.529], but all subarctic populations were fixed for a single mitotype (HE = 0). This lack of variation suggests a founder event caused by long-distance seed establishment during postglacial colonization, consistent with palaeoecological data. The estimated movement of seeds alone (effective number of migrants per generation, NmM < 2) was much restricted compared to that estimated from nuclear variants, which including pollen movement (NmN > 17). This could account for the conservation of a founder imprint in the mtDNA of subarctic black spruce. After reduction, presumably in the early Holocene, the diversity in ncDNA would have been replenished rapidly by pollen-mediated gene flow, and maintained subsequently through vegetative layering during the current cooler period covering the last 3000 years.

DNA, Mitochondrial↗
PubMed2002

The legacy of nuclear risk and the founder effect in biotechnology organizations.

In the wake of the Chernobyl nuclear accident and a decline in the public trust of science, the founders of modern biotechnology recognized the strategic importance of risk assessment and regulatory affairs. In an effort to avoid the demonization that was attached to the nuclear industry, the pioneers of modern biotechnology delegated authority for regulatory negotiation and risk management to senior positions in the firm. At the same time, the Biotechnology Industry Organization was handed great latitude and trust with making public pronouncements on issues of bioethics and public policy. The way in which founders and leaders embed norms for negotiating regulation and responding to public perceptions has proved important in the maturation and acceptance of a biotechnology sector.

Biotechnology↗
PubMed1988

The founder effect theory: quantitative variation and mdg-1 mobile element polymorphism in experimental populations of Drosophila melanogaster.

One of the main points of Mayr's 'founder's principle' is the role played by inbreeding in the first generations after the foundation of a population. To test this role, we studied 10 experimental populations of Drosophila melanogaster, each founded by one brother-sister pair; these sib pairs differed for their values of viability components of their F1 offsprings. The populations so formed were maintained en masse with non-overlapping generations. Under our uniform laboratory environmental conditions, the mean viability and within-family component of variance (measured on wing length) values of the first generations depended on the viability component values of the founders. After about twenty generations, all but one of these populations reached equilibrium values similar to those of the parental population. Moreover, the insertion patterns of the mdg-1 mobile element were analysed in the founded populations by in situ hybridization on polytene chromosomes. The patterns differed between the founded populations. More than forty generations were needed before movements of transposable elements reshaped the genome in a significant way. Although it is classically admitted that inbreeding resulting from founder event ultimately leads to extinction, our results show that once the first generations are over, the founded populations become firmly established and present the characteristics of the parental population.

Animals↗
PubMed1988

Founder effect and genetic disease in Sottunga, Finland.

Pedigree data are analyzed in order to determine the factors responsible for the high frequencies of certain genetic disorders in an isolated Swedish-speaking population of Finland's A land archipelago. The founders of Sottunga are identified, and the genetic contributions of each founder to descending birth cohorts are estimated. Founders born before 1700 have far more descendants in the contemporary gene pool than do more recent founders. However, because of migration and depopulation since 1900, the expected genetic contributions of the early founders to the present-day population are similar to those of later founders. A descendant in the contemporary population has a 2% chance of having inherited a particular gene from the founder who makes the largest single contribution to the gene pool. This corresponds approximately to a 2% probability of inheriting an autosomal dominant disease gene from this founder. Given an average inbreeding coefficient of 0.0016, the probability of inheriting two recessive disease genes from this founder is 0.000032. The incidence of autosomal dominant von Willebrand disease in Sottunga is greater than 10% while that of autosomal recessive tapetoretinal disease is 1.5%. We conclude, therefore, that the high frequencies of these diseases are not due to the disproportionate genetic contribution of one or a few particular founders. It is more likely that these disease genes occurred in high frequency in the initial population or were introduced repeatedly through time.

Finland↗
PubMed1991

Founder effect in familial hyperchylomicronemia among French Canadians of Quebec.

Familial hyperchylomicronemia has reached a high prevalence in the French Canadian population of eastern Quebec. The birth places of 58 carriers identified through the birth of one affected child clustered in three regions. The genealogies of these 58 individuals showed that no founder was common to all of them. Three sets of founders were found, one for each region, with little overlapping between two regions. These results strongly suggest that more than one mutation, introduced by the French migrants in the 17th century, are segregating in the French Canadian population. Perche, a region situated between Paris and Normandy, appeared to be the most likely putative center of diffusion of at least one mutation in the lipoprotein lipase gene segregating in the modern-day French Canadian population of Quebec.

France↗
PubMed1993

Founder effect in beta-thalassaemia in Portneuf, Québec.

The genealogies of seven individuals with beta-thalassaemia minor carrying the (beta+IVS-1, nt110) mutation were reconstructed to determine the origin of the mutation in the French Canadian population of Portneuf County. A set of 55 ancestors common to all seven carriers was defined. These founders included 38 born in Europe of whom 34 came from 13 different regions of France and in particular from Languedoc (2 ancestors), a French province along the Mediterranean sea in which the mutation is still present. Descendants of these two individuals settled in Portneuf County where the gene frequency increased due to a high level of endogamy. However, present results cannot exclude a possibility that the (beta+IVS-1, nt110) mutation was introduced into the French Canadian population by settlers originating from a non-malarial region of France. The beta-thalassaemia gene has since spread from Portneuf County over the last century.

Female↗
PubMed1991

Founder effect in 20 Afrikaner kindreds with pseudoxanthoma elasticum.

The pedigrees of 20 families with pseudoxanthoma elasticum (PXE) were investigated. The analyses involved 13 generations up to and including the initial settlers, who arrived in the Cape before 1660. Four settler surnames predominate in these pedigrees. Because of the marriage patterns of the settlers' descendants it was necessary to classify the four surnames into two groups. It is suggested that these two groups are the founder groups of present-day PXE patients. Similar genealogical studies have been performed on kindreds with familial polyposis, familial heart block and familial hypercholesterolaemia, among other disorders. Due to geographical isolation, political developments and cultural factors in the Afrikaner, these investigations are feasible and often lead to the identification of founder origin.

Female↗
PubMedDate not supplied

Founder effects and the genetic structure of Coulter pine.

Mean expected heterozygosity at 33 isozyme loci decreased with latitude from 0.193 near the southern extreme of Coulter pine's range to 0.107 at its northern extreme. This decrease was paralleled by a loss of alleles north of the Peninsular Ranges of southern California. Fifteen alleles dropped out along the roughly lineal range, at points coincident with large gaps in the species' distribution. The pattern may reflect a cascading series of founder events as Coulter pine invaded the Trans. verse Ranges and the South Coast Ranges from Pleistocene refugia. Alleles were not replaced following colonization, probably because migration, Nm, among populations is only 0.74-1.27, depending on estimator, the lowest values reported in any pines. Wright's (F(ST)) indicated that 16.5% of the total genic diversity is among populations. The fixation index, (F(IS)) of 0.072 indicated only a moderate excess of homozygotes. However, the northernmost outlier had significant excess homozygosity (F = 0.253). Hybridization may also play a role in the genetic structure of Coulter pine: 16 alleles were novel, or private, occurring only where Coulter pine was sympatric with Jeffrey pine, particularly at San Benito Mountain. Some of these novel alleles could be the result of introgression from Jeffrey pine, or possibly represent hybrizymes, products of intragenic recombination between genomes.

Alleles↗
PubMed2004

Familial ALS in Germany: origin of the R115G SOD1 mutation by a founder effect.

Mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1) account for approximately 20% of patients with familial amyotrophic lateral sclerosis (FALS). In this study, sequence analysis of exons 1-5 of SOD1 in a large German cohort with FALS was performed. Among 75 affected patients, who were not obviously related probands with a positive family history, nine had missense mutations in SOD1. Four of the nine probands carry the same R115G mutation in exon 4 of the SOD1 gene. Genotyping with markers from the SOD1 locus revealed a common haplotype and shared allelic characteristics in these patients. These findings suggest that the R115G mutation in the German population originates from a common founder.

Adult↗
PubMed1985

Dramatic founder effects in Amerindian mitochondrial DNAs.

Southwestern American Indian (Amerindian) mitochondrial DNAs (mtDNAs) were analyzed with restriction endonucleases and found to contain Asian restriction fragment length polymorphisms (RFLPs) but at frequencies very different from those found in Asia. One rare Asian HincII RFLP was found in 40% of the Amerindians. Several mtDNAs were discovered which have not yet been observed on other continents and different tribes were found to have distinctive mtDNAs. Since the mtDNA is inherited exclusively through the maternal lineage, these results suggest that Amerindian tribes were founded by small numbers of female lineages and that new mutations have been fixed in these lineages since their separation from Asia.

Asia↗
PubMed2006

Parkinson's disease due to the R1441G mutation in Dardarin: a founder effect in the Basques.

The recent discovery of mutations in Dardarin (LRRK2) have been related to the appearance of Parkinson's disease in several families. Notably, one single mutation in this gene (R1441G) not only appeared in familial, but also in apparently sporadic Parkinson disease (PD) patients of Basque descent. A clinical population was ascertained, and subjects were classified into Basque and non-Basque descent according to their known ancestry. The R1441G mutation was assayed using an allele-specific polymerase chain reaction, and several single nucleotide polymorphisms surrounding this mutation were analyzed by direct sequencing. In addition to 22 members of the original Basque families where R1441G was identified, we observed 17 carriers of the mutation who were apparently related through a common ancestor. From a clinical perspective, the disease observed in mutation carriers is indistinguishable from that in noncarriers. The R1441G mutation causes a form of Parkinson's disease that is equivalent to that observed in idiopathic Parkinson's disease. This mutation appears in 16.4% and 4.0% of familial and sporadic PD in this Basque population, respectively.

Aged↗
PubMed1991

T296----M, a common mutation causing mild hemophilia B in the Amish and others: founder effect, variability in factor IX activity assays, and rapid carrier detection.

By direct genomic sequencing, we have delineated the causative mutation in 64 families of European decent with hemophilia B. Six (9%) had a C----T transition at base 31008, which substitutes methionine for threonine 296 (T296----M) in the catalytic domain of factor IX. Five of the patients had the same haplotype (frequency of 16% in the northern European population). These individuals are of Amish/German descent and they are likely to share a common ancestor. The sixth patient had a different haplotype, which indicates that his mutation had an independent origin. The data highlight the importance of clinical criteria for the classification of hemophilia B. All six patients had clinically mild disease and their factor IX coagulant activities were in the range of 3%-6% when tested simultaneously in one laboratory, yet the factor IX activities provided with patient records varied 40-fold. Due to the high frequency of this mutation, we have utilized the technique of polymerase chain reaction amplification of specific alleles (PASA) to perform rapid and inexpensive carrier diagnoses in the families with this mutation. This is of particular importance for the Amish since the mutation should account for much of, if not all, the mild hemophilia B that is commonly found in this population.

Base Sequence↗
PubMed1993

Recurrent mutations in the factor IX gene: founder effect or repeat de novo events. Investigation of the German haemophilia B population and review of de novo mutations.

The investigation of 114 unrelated patients, representing about half the sample of the German haemophilia B population, enabled us to delineate the causative mutation in 103 (90.4%) haemophilic factor IX genes. Of these 103 cases 84 (81.6%) turned out to be unique molecular events, the remainder being repeats. Haplotype analysis revealed that the great majority, if not all, of these recurrent observations occurred independently. This conclusion is supported by our finding that three de novo mutations could be demonstrated at two sites of frequent mutation. A further 20 de novo events could be established in an unselected sample of 37 families with sporadic haemophilia B and 37 families with a history of the disease. Altogether, the germ line of origin could be determined in 21 of these 23 cases, thereby indicating a ratio of male to female mutation rates close to 2. On the basis of the data available, it is becoming clear that rearrangements in the factor IX gene (35.4% of de novo cases) are responsible for haemophilia B at a higher frequency than has been observed today (12.3%). More than two-thirds of the de novo cases cause the severe form of the disease, thereby reflecting the deficit of these haemophilic genes in the actual gene pool because of excess mortality in the past. In addition 40% (12/30) of the de novo single-base mutations were transitions at CpG dinucleotides. Compared with the expected at-random frequency, this observation indicates an 83-fold enhancement of mutation at CpG.

DNA Mutational Analysis↗