Population genetics - Founder effect problem solution

In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall Wright. As a result of the loss of genetic variation, the new population may be distinctively different, both genotypically and phenotypically, from the parent population from which it is derived. In extreme cases, the founder effect is thought to lead to the speciation and subsequent evolution of new species. In the figure shown, the original population has nearly equal numbers of blue and red individuals. The three smaller founder populations show that one or the other color may predominate (founder effect), due to random sampling of the original population. A population bottleneck may also cause a founder effect even though it is not strictly a new population. The founder effect occurs when a small number of migrants that are not genetically representative of the population from which they came establish in a new area. In addition to founder effects, the new population is often a very small population and so shows increased sensitivity to genetic drift, an increase in inbreeding, and relatively low genetic variation. This can be observed in the limited gene pool of Iceland, Faroe Islands, Easter Islanders and those native to Pitcairn Island. Another example is the legendarily high deaf population of Martha’s Vineyard, which resulted in the development of Martha’s Vineyard Sign Language. Due to various migrations throughout human history, founder effects are somewhat common among humans in different times and places. The French Canadians of Quebec are a classical example of founder population. Over 150 years of French colonization, between 1608 and 1760, it was estimated that 8,500 pioneers married and left at least one descendent on the territory. Following the takeover of the colony by the British crown in 1760, immigration from France effectively stopped, but descendents of French settlers continued to grow in number mainly because of high fertility rate. Intermarriage occurred mostly with the deported Acadians and migrants coming from the British Isles. Since the 20th century, immigration in Quebec and mixing of French Canadians involve people from all over the world. While the French Canadians of Quebec today may be partly of other ancestries, the genetic contribution of the original French founders is predominant, explaining about 90% of regional gene pools, while Acadians (descended from other French settlers in eastern Canada) explain 4%, British 2% and Native American and other groups contributed less. Founder effects can also occur naturally as competing genetic lines die out. This means that an effective founder population consists only of those whose genetic print is identifiable in subsequent populations. Because in sexual reproduction, genetic recombination ensures that with each generation, only half the genetic material of a parent is represented in the offspring, some genetic lines may die out entirely, even though there are numerous progeny. The misinterpretations of “Mitochondrial Eve“ are a case in point: it may be hard to explain that a “mitochondrial Eve“ was not the only woman of her time. In humans, founder effects can arise from cultural isolation, and inevitably, endogamy. For example, the Amish populations in the United States exhibit founder effects. This is because they have grown from a very few founders, have not recruited newcomers, and tend to marry within the community. Though still rare, phenomena such as polydactyly (extra fingers and toes, a symptom of Ellis-van Creveld syndrome) are more common in Amish communities than in the American population at large. Maple syrup urine disease (MSUD) affects approximately 1 out of 180,000 infants in the general population. Due in part to the founder effect, however, the disease has a much higher prevalence in children of Amish, Mennonite, and Jewish descent. Similarly, there is a high frequency of fumarase deficiency among the 10,000 members of the Fundamentalist Church of Jesus Christ of Latter Day Saints, a community which practices both endogamy and polygyny, where it is estimated 75 to 80 percent of the community are blood relatives of just two men—founders John Y. Barlow and Joseph Smith Jessop. #alleles #offspring #Diploid #Genetics101 #geneticVariation #recessive #dominant #PaternityTest #originalPopulation #autosomal #genotype #culturalIsolation #founderPopulations #GeneticExamQuestionsSolutions #PopulationGenetics #parentPopulation #GeneticsLecture #Allele #MolecularBiology #GeneticTesting #RNA #Genetics #GeneticsExamQuestionsSolutions #AllelicFrequencies