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Croze, Myriam Florence (2017): A genome-wide scan for genes under balancing selection in Drosophila melanogaster. Dissertation, LMU München: Fakultät für Biologie
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Abstract

In the history of population genetics balancing selection has been considered as an important evolutionary force, yet until today little is known about its abundance and its effect on patterns of genetic diversity. Several well-known examples of balancing selection have been reported from humans, mice, plants, and parasites. However, only very few systematic studies have been carried out to detect genes under balancing selection. We performed a genome scan in Drosophila melanogaster to find signatures of balancing selection in a derived (European) and an ancestral (African) population. We screened a total of 34 genomes searching for regions of high genetic diversity and an excess of SNPs with intermediate frequency. In total, we found 186 candidate genes: 141 in the European population and 45 in the African one, with only three genes shared between both populations. The difference between both populations is mainly due to a striking excess of candidate genes on the European X chromosome. For the European population, many GO terms are enriched including a main group of which many genes are related to cell morphogenesis involved in differentiation. Furthermore, some of the top genes we identified are involved in innate immunity. However, only two GO terms are found in the African population. Our results revealed evidence of genes under balancing selection in European and African populations. More candidate genes, in particular on the X chromosome, have been found in the European population. They are involved in many different functions.