Molecular Evolution of Drosophila Y Chromosome

描述（由申请人提供）：Y染色体提供了一个不寻常的 有机会研究人口遗传过程，如搭便车， 背景选择，因为它的重组隔离从其他 染色体，其有效的单倍体传递，以及其对 男性。果蝇Y染色体群体遗传学研究进展 我们对蛋白质编码基因和单拷贝基因的无知， 顺序通过使用与正常方法相反的BLAST，我们有 成功鉴定了8个新的蛋白质编码基因在Y染色体上， D.黑腹菌我们现在能够提供一个全面的量化 的Y染色体上的变异模式。黑腹，并放置 这与相关物种的种间序列差异有关。 四个相互竞争的模型，并不完全相互排斥， Y染色体上的变异水平。他们是穆勒的棘轮，背景 选择、希尔-罗伯逊效应和搭便车。所有四个导致 预测Y上的长期变化水平应该被压低 但它们对发生频率的说法不同 谱、群体细分程度和等位基因的年龄分布。我们 建议参数化和定量权衡这些优点， 竞争的假设通过以下三个目标：首先，我们将量化 和Y染色体上蛋白质编码基因的种内多态性模型 D.通过dHPLC和直接测序的组合检测黑腹菌 在一组96个Y染色体置换系中的Y连锁蛋白编码基因 全球分布。其次，我们将从一个 一系列相关物种，以确定分歧率， 描述内含子Y异染色质的分子进化。最后我们 将测试分离Y染色体变异和精子变异之间的联系 通过精子运动学分析和精子竞争性试验 能力这些研究将建立D.黑腹动物作为一个关键的实验 Y染色体多态性和分子进化分析系统。

DESCRIPTION (provided by applicant): The Y chromosome provides an unusual opportunity to examine population genetic processes like hitchhiking and background selection because of its recombinational isolation from other chromosomes, its effectively haploid transmission, and its restriction to males. Progress in studying Y chromosome population genetics of Drosophila has been held back by our ignorance of protein-coding genes and single-copy sequence. By using BLAST in the reverse of the normal approach, we have successfully identified eight new protein-coding genes on the Y chromosome of D. melanogaster. We are now in a position to provide a thorough quantification of patterns of variation on the Y chromosome of D. melanogaster, and to place this in the context of interspecific sequence divergence with related species. Four competing models, not all mutually exclusive, make predictions about levels of variation on a Y chromosome. They are Muller's ratchet, background selection, the Hill-Robertson effect, and hitchhiking. All four lead to the prediction that standing levels of variation on the Y ought to be depressed compared to autosomes, but they make different claims about the frequency spectrum, degree of population subdivision, and age distribution of alleles. We propose to parameterize and to quantitatively weigh the merits of these competing hypotheses through the following three aims: First, we will quantify and model intraspecific polymorphism in protein-coding genes on the Y chromosome of D. melanogaster by a combination of dHPLC and direct sequencing of Y-linked protein-coding genes in a set of 96 Y chromosome replacement lines of global distribution. Second, we will obtain corresponding sequences from a series of related species, in order to determine divergence rates and to characterize the molecular evolution of intronic Y heterochromatin. Finally, we will test associations between segregating Y variation and variation in sperm function through sperm kinematics assays and tests of sperm competitive ability. These studies will establish D. melanogaster as a key experimental system for analysis of Y chromosome polymorphism and molecular evolution.