Studies on mechanism of maintenance of DNA polymorphism and statistical methods for analyzing DNA polymorphism data

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Natural populations have a large amount of genetic variation at the DNA level. How much and why such genetic variation is maintained in a population is one of the most important questions in population genetics. A large number of possible mechanisms were proposed, such as neutral theory, slightly deleterious model, hitchhiking model, overdominance model and frequency dependent model. In this research project, I have worked on this subject and obtained the following results.IN order to understand the mechanism of maintenance of DNA polymorphism, I have studied the case of non-random mating population and obtained new model : two subpopulations were partially separated t1 generations ago and these two subpopulations were completely separated t2 generations ago.The relationship between natural selection and population structure were examined in terms of the mechanism of maintenance of DNA polymorphism. Using the finite island model, the following results were obtained. The effect of dominance on the amount of DNA polymorphism decreases as the migration rate decreases and the effect disappears when the migration rate is extremely low. Using the same model, the rate of molecular evolution was studied. The results indicate that the effect of dominance on the rate of molecular evolution decreases as the migration rate decreases, but the effect does not disappear even when the migration rate becomes extremely low. This means that the degree of dominance affects differently between the amount of DNA polymorphism and the rate of molecular evolution.