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Some Case Histories
Published in Jacques Derek Charlwood, The Ecology of Malaria Vectors, 2019
The only haplotype that matched that found in São Tomé comes from an Angolan population. It is therefore probable that this was the source of the local population. Slaves were also taken to STP from Angola so it is likely that the mosquito arrived with them. Thus, although in many regions A. coluzzii is associated with drier environments, it also thrives in the humid environment of São Tomé. A founder effect, in which the established population is derived from a small number of genotypes that do not cover all of the available genotypes in the species, is evident in the population from the islands.
Setting the scene
Published in Jessica Mozersky, Risky Genes, 2012
The founder effect is a process of genetic drift that results from a founder event. A founder event occurs when a population has a small number of founding ancestors who are separated from the larger parent population and go on to found a new population (Stone et al. 2007). Alternatively, a founder event can be the result of an extreme reduction of a population, by over 50 per cent, due to famine, war, epidemic or some other event that causes a significant number of a population's members to die. This is known as population bottleneck because the population suddenly contracts. In both of these situations, the new founding population carries only a fraction of the original population's genetic variation and is not representative of the entire diverse population from which it was derived but only a small portion of it (Goldstein 2008, Stone et al. 2007). As a result this new population can be quite distinct from the original population. The founder effect occurs when at least one of the members of the new founding population carries a genetic mutation which is then passed on to future generations. The mutation may substantially increase in frequency if the population remains reproductively closed, for example due to cultural practices such as endogamy. Members of founding populations tend to live in close geographic proximity and so are more likely to mate with one another, which will increase the frequency of the mutation as the population increases in size (Bamshad et al. 2004).
Characterization of population genetic structure of hereditary transthyretin amyloidosis in Bulgaria
Published in Amyloid, 2021
Zornitsa Pavlova, Stayko Sarafov, Tihomir Todorov, Andrey Kirov, Teodora Chamova, Mariana Gospodinova, Ivailo Tournev, Vanyo Mitev, Albena Todorova
The individual haplotypes for each of the three ATTRv amyloidosis family groups (Val30Met, Ser77Phe and Gly47Glu) were theoretically reconstructed and the prevalence of the most common haplotypes was compared within the subgroups of patients and non-carrier healthy relatives. The most common haplotype for each TTR variant is shown in Table 3. The alleles, building the prevalent reconstructed haplotypes for the Val30Met, Ser77Phe and Gly47Glu variants are distributed with higher frequency in the patient groups compared to the healthy non-carrier relatives and the control individuals (Table 4). Based on the observed frequencies, the three reconstructed haplotypes could be considered hypothetical founder haplotypes for each variant respectively. Further statistical analysis for the significance of the proposed founder effect hypothesis was performed based on the frequencies of the hypothetical founder STR alleles in the TTR pathogenic variant group compared to the healthy relatives’ group for each TTR variant respectively. The results from the Pearson’s Chi-square test of independence are shown in Table 5. The corresponding p-values for the hypothetical founder haplotype alleles are considered at an alpha level of significance .05 and the analysis showed an association of the tested variables. This accepts the hypothesis for founder effect for the Val30Met, Ser77Phe and Gly47Glu TTR pathogenic variants.
Understanding the genetic pathology of Stargardt disease: a review of current findings and challenges
Published in Expert Opinion on Orphan Drugs, 2021
David A. Camp, Michael C. Gemayel, Thomas A. Ciulla
There is geographic/ethnic variability in mutation frequencies due to founder effect. STGD1 has been shown to be associated with p.(Gly1961Glu) and p.(Ala1038Val) variants in Euro-American descendants and with p.(Arg1129Leu) in Spanish patients [26,31,75]. In Sweden, an estimated 5.5% of the population carries the p.(Gly863Ala,Gly863del) variant [72]. In Somalia, an estimated 11.3% of the population carries the p.(Gly1961Glu) variant [76]. In 44 African American patients with ABCA4-associated retinopathy (41 with STGD1), c.6320 G > A (p.(Arg2107His)) was the most common ABCA4 genetic variation (19.3%) [77]. Other common variations with geographic/ethnic associations include complex allele p.(Leu541Pro; Ala1038Val) in patients with German heritage [32,78], p.(Arg1129Leu) in Spain [79], p.(Asn965Ser) in the Danish population [80], p.(Ala1773Val) in Mexico [81], p.(Leu541Pro;Ala1038Val) in Poland [82], and c.(1761–2A>G) in Western China [83].
Founder effect of the Glu89Gln TTR mutation in the Bulgarian population
Published in Amyloid, 2019
Andrey Kirov, Stayko Sarafov, Zornitza Pavlova, Tihomir Todorov, Teodora Chamova, Mariana Gospodinova, Ivailo Tournev, Vanyo Mitev, Albena Todorova
The founder effect usually causes linkage disequilibrium between alleles of certain loci inherited from the founder individual. This phenomenon explains the difference between the observed allele frequencies of a particular haplotype and the frequencies expected for a random association of alleles. The L4 and L8 markers are in a relatively close proximity to the Glu89Gln mutation which theoretically determines lower recombination rate and haplotype decay proceeding at a slower pace. On the contrary, as the distance from the mutation increases, the probability for haplotype decay is getting higher. The L4 and L8 hypothetical founder alleles (267 bp and 292 bp) are represented with highest frequency in our mutation carrier group. The observed frequency is decreasing with increase of the distance from the mutation, except for the D18S46 marker. The latter might be explained with past recombination events.