Evolution of the retrotransposons R1 and R2

R1和R2是大多数节肢动物28S核糖体RNA基因片段中插入的序列特异性反转录转座元件。这一提议的目的是确定这些元素的显著成功是由于它们在物种之间的自由迁移还是它们在物种谱系中长期保持活跃的能力。大多数实验将集中于从双翅目果蝇属物种中分离的R1和R2的序列关系。经聚合酶链反应扩增并确定其核苷酸序列后，克隆出3′半的元件。该序列分析将与利用基因组DNA印迹方法研究R1和R2在几个物种的不同地理菌株中的分布相补充。实验还将对三种寄生蜂（Nasonia属）进行，它们包含多个高度分化的R1元素家族。拟议的实验将为理解基因组内可移动元件的稳定性、它们在物种之间转移的能力以及它们调节自身丰度的能力提供基础信息。

R1 and R2 are sequence-specific retrotransposable elements found inserted in a fraction of the 28S ribosomal RNA genes of most arthropods. The objective of this proposal is to determine whether the remarkable success of these elements is due to their freedom to move from species to species or their ability to remain active in a species lineage over long evolutionary periods. Most experiments will focus on the sequence relationships of R1 and R2 isolated from species of the dipteran genus Drosophila. The 3' half of the elements will be cloned after the polymerase chain reaction amplification and their nucleotide sequences determined. This sequence analysis will be complemented with studies of the distribution of R1 and R2 within different geographical strains of several species using genomic DNA blotting procedures. Experiments will also be conducted with three species of parasitic wasp (genus Nasonia) which contain multiple families of highly divergent R1 elements. %%% The proposed experiments will provide information that is fundamental to an understanding of the stability of mobile elements within genomes, their ability to transfer between species, and their ability to regulate their own abundance.