A Study of Molecular Population Genetics on the Aspect of Edaptive evolution in Drosphila

在基因分子数据的积累过程中，中性分子进化理论（Kimura, 1968）的概率性已被人们所接受。Mukai和他的同事们已经证明，大多数蛋白质多态性是选择性中性的。本研究的目的是在分子水平上研究遗传变异，即适应性进化的来源，并证明中性理论是否适用于这些实验数据。在这项研究中，以下事情变得清晰起来。1. 我们已经证明，在生存力的加性遗传变异中存在从北向南的倾斜。这表明一些平衡选择在这些变异种群中起作用。我们研究了北（Amori）和南（Ogasawara）人群4个基因区域（Adh、Amy、Gpdh、Punch）的限制性内切酶南部多态性。限制性内切位点多态性差异不显著，但插入、多位点和缺失位点多态性差异显著。在南方人群中观察到很大的差异。这一事实可能表明，北方人口中过多的加性遗传变异反映了这些变异的累积效应。2. 发现Gpdh基因的重复或三倍是多态的。指出基因复制是基因进化的重要机制。这些变异似乎是在突变发生和净化选择或随机遗传漂变之间的平衡中维持的。此外，我们还获得了这些基因通过不平等杂交以协调方式进化的证据。3. 转座因子占果蝇基因组的10%左右，它们经常产生复杂的突变。转位率是评价这些突变对适应进化的贡献的重要参数之一。利用突变积累线，我们估计了几个转座因子的转座率。这是此类估计中第一个可靠的。4. 我们比较了几个转座因子在南方和北方人群中的分布。一些相似的元素在两个种群中表现出数量上的差异。5. 我们研究了与P元素活性和分子结构有关的种群结构。我们得到的证据表明，在P元素入侵的过程中，会引起大量的遗传负荷。P元素的长度有变化。全尺寸元素的分布在种群间存在差异，但类KP元素的频率在所有种群中都呈增加趋势。少

The generality of the neutral theory of molecular evolution (Kimura, 1968) has been accepted in the course of accumulation of molecular date of genes. Mukai and his colleagues have shown that most of the protein polymorphisms are selectively neutral. The purpose of this study is to investigate the genetic variation, that is the source of adaptive evolution, in molecular level and testify whether the neutral theory is operational for these experimental data.Following things have become clear in this study. 1. We have shown that there is north to south cline in the additive genetic variance in viability. This is suggesting some of balancing selection is operating on these variations population. We studied restriction enzyme in southern polymorphism in four gene regions (Adh, Amy, Gpdh, Punch) in north (Amori) and south (Ogasawara) populations. There is no significant difference in restriction site polymorphisms, but significant difference was detected in the polymorphisms in insertions a … More nd deletions. Large amount of difference was observed in the southern population. This fact may suggest that excess additive genetic variance in the northern population is reflecting the cumulative effect of these variations. 2. The duplication or triplication of Gpdh gene is found to be polymorphic. It is pointed that gene duplication is important mechanism of gene evolution. These variation appeared to be maintained in the balance between mutational occurrence and purifying selection or by random genetic drift. Furthermore, we obtained an evidence that these genes evolved in concerted fashion by unequal crossing-over. 3. Transposable elements occupy about 10% of Drosophila genome and they often create complicated mutations. Transposition rate is one of the important parameter in evaluating the contribution of these mutations to adaptive evolution. Using mutation accumulation lines, we estimated transposition rates of several transposable elements. This the first reliable of such estimations. 4. We compared the distribution of several transposable elements in southern and northern populations. Some copia like elements shows difference in number between two populations. 5. We investigated the population structure concerning to P element activity and molecular structure. We obtained an evidence that in the course of invasion of P element, it causes large amount of genetic loads. There is variation in the length of P element. There is interpopulational difference in the distribution of complete size elements, but the frequency of KP like elements is increasing in all the populations investigated. Less