Population Genetics of Transposable Elements

遗传学领域最近有一项令人兴奋的发现，从细菌到人类的生物体基因组中都含有一些能够自我复制的DNA序列，这些DNA序列可以插入基因组的其他地方。这些被称为转座因子（te）。将TE插入或靠近基因可能导致突变，对个体的生存能力或生育能力产生有害影响。例如，在人类中，TE插入与引起血友病和乳腺癌的突变有关。TEs的发现引发了一场关于控制TEs在其宿主物种种群内分布的力的本质的辩论。先前对果蝇、酵母和细菌的研究表明，尽管宿主个体的基因组中可能存在同一TE家族成员的几个拷贝，但不同个体的拷贝数量可能不同。此外，这些通常被发现插入到不同宿主个体的不同位置，这表明某种力量阻止了TE填充基因组内所有可用的位置。目前的研究旨在帮助确定这些力的性质，将收集果蝇种群中TE分布的进一步数据，并与理论模型的预测进行比较。这将检验上述观察结果的普遍性。此外，还将对TEs在基因重组受到限制的基因组区域积聚的趋势进行检测。这种倾向是由位于不同位置的同源TE之间的遗传交换可以产生染色体损伤，从而消除相关TE，从而阻止其扩散的假设预测的。其中一个区域被称为中心异染色质。由于技术上的困难，该区域高度重复的DNA序列丰富，因此以前没有对该区域进行详细研究。DNA技术的最新进展意味着现在有可能研究异染色质中的TE丰度，这形成了该项目的主要焦点。

An exciting recent finding of genetics has been the discovery that the genomes of organisms from bacteria to humans contain families of DNA sequences that have the ability to make new copies of themselves that can insert elsewhere in the genome. These are known as transposable elements (TEs). The insertion of a TE into or near a gene may cause a mutation with a harmful effect on the survival ability or fertility of the individual. For example, in humans TE insertions have been implicated in mutations causing hemophilia and breast cancer. The discovery of TEs has led to a debate on the nature of the forces that control the distribution of TEs within populations of their host species. Previous studies in Drosophila, yeast and bacteria have shown that, although several copies of members of the same family of TE may be present within a host individual's genome, different individuals may have different numbers of copies. Furthermore, these are generally found to be inserted into different places in different host individuals, suggesting that some force of forces are preventing TE's from filling up all the sites available for occupation within the genome. The present study is designed to help identify the nature of these forces Further data on the distribution of TE's within a population of Drosophila will be collected and compared with the predictions of theoretical models. This will provide a check of the generality of the observations mentioned above. In addition, tests will be made of the tendency of TEs to accumulate in regions of the genome where genetic recombination is restricted. Such a tendency is predicted by the hypothesis that genetic exchange between homologous TE's located in different locations can produce chromosomal damage that eliminates the TEs concerned, and hence acts to prevent their spread. One such region is known as the centric heterochromatin. This region has not previously been studied in detail because of technical difficulties associated with the abundance of highly repeated DNA sequences in this region. Recent advances in DNA technology mean that it is now possible to study TE abundance in the heterochromatin, and this forms a major focus of the project.