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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 group of migrants that is 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 pools of Icelanders, Ashkenazi Jews, Faroe Islanders, Easter Islanders, Filipinos, and those native to Pitcairn Island. Another example is the remarkably high deaf population of Martha's Vineyard, which resulted in the development of Martha's Vineyard Sign Language. ==Founder mutation== In genetics, a founder mutation is a mutation that appears in the DNA of one or more individuals who are founders of a distinct population. Founder mutations initiate with changes that occur in the DNA and can be passed down to other generations.〔(【引用サイトリンク】title=Bioinformatics Glossary ) 〕〔(【引用サイトリンク】title=Colorectal Cancer Research Definitions ) 〕 Founder mutations originate in long stretches of DNA on a single chromosome—indeed, the original haplotype is the whole chromosome. As the generations progress, the proportion of the haplotype that is common to all carriers of the mutation is shortened (due to genetic recombination). This shortening allows scientists to roughly estimate the age of the mutation.〔 (【引用サイトリンク】title=Founder Mutations: Scientific American ) 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Founder effect」の詳細全文を読む スポンサード リンク
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