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Amylase gene variability in human populations
Vosmíková, Veronika ; Černý, Viktor (advisor) ; Daňková, Pavlína (referee)
Amylase is a starch-digesting enzyme produced by the pancreas and salivary glands in humans. Genes for the salivary isoenzyme (AMY1), located on chromosome 1p21.1, show remarkable variability in their copy numbers (CNV). Their count is positively correlated with the final amount of the produced enzyme. This variability could be the result of positive selection during human evolution, depending on the amount of starch consumed by various populations. Starch pre-digested by salivary α-amylase is absorbed more effectively, resulting in a greater gain of energy in later stages of the metabolizing process. Thus, it could have been one of the factors for rapid brain growth in humans and, significantly later, even for the agricultural transition. It could belong to a group of other known subsistence-based evolutionary changes in the human genome, such as those resulting in lactase persistence or slow acetylation of xenobiotics. Nowadays, the number of copies and the amount of produced α-amylase can influence the glucose level in the blood and insulin production after consumption, as well as the incidence of certain civilization diseases, such as obesity or type II diabetes. The influence of salivary α-amylase on the composition of the microbiome, cardiovascular diseases, and the pro-inflammatory profile...
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Role of genetic variance in speciation
Payne, Pavel ; Markoš, Anton (advisor) ; Rueffler, Claus (referee)
Sympatric speciation has received much attention both empirically and theoretically. However, the contribution of sympatric speciation to biodiversity remains unclear. One piece missing from the speciation puzzle is the plausibility of sympatric ecological divergence of species through adaptation in polygenic traits. I consider an environment consisting of two niches, where one value of the trait is advantageous in only one niche, and vice versa. The selection regime is described by a trade-off in viabilities between the niches. These polygenic traits can, and often do, involve epistatic interactions among and between loci, so that the contribution of the alleles to viability deviates from additivity. Epistasis then also affects the curvature of the trade-offs: predominant less-than-additive epistasis turns the curve towards concavity and predominant more-than-additive towards convexity. The curvature of the trade-off plays a crucial role in the evolution of populations. With a convex trade- off, extreme values of the trait are favored and the population tends to diverge, but relatively stringent symmetry in strength of selection within the niches and the niche proportions is necessary to maintain polymorphism. In this study I use two and three- locus haploid versions of Levene's model to...
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Role of genetic variance in speciation
Payne, Pavel ; Markoš, Anton (advisor) ; Rueffler, Claus (referee)
Sympatric speciation has received much attention both empirically and theoretically. However, the contribution of sympatric speciation to biodiversity remains unclear. One piece missing from the speciation puzzle is the plausibility of sympatric ecological divergence of species through adaptation in polygenic traits. I consider an environment consisting of two niches, where one value of the trait is advantageous in only one niche, and vice versa. The selection regime is described by a trade-off in viabilities between the niches. These polygenic traits can, and often do, involve epistatic interactions among and between loci, so that the contribution of the alleles to viability deviates from additivity. Epistasis then also affects the curvature of the trade-offs: predominant less-than-additive epistasis turns the curve towards concavity and predominant more-than-additive towards convexity. The curvature of the trade-off plays a crucial role in the evolution of populations. With a convex trade- off, extreme values of the trait are favored and the population tends to diverge, but relatively stringent symmetry in strength of selection within the niches and the niche proportions is necessary to maintain polymorphism. In this study I use two and three- locus haploid versions of Levene's model to...
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