Molecular Population Genetics of Duplicated Genes in Drosophila.

在高等生物的基因组中存在着大量的重复基因，其中包括转座因子。本课题主要研究果蝇淀粉酶系统适应性进化的分子机制以及转座因子I的进化。通过对果蝇种亚组8个姊妹种重复Amy基因的核苷酸序列分析，发现重复位点之间具有很强的种内相似性，与此相反，在整个物种亚群中，每个基因座（近端或远端）的5'和3'侧翼区具有很强的相似性。这一结果表明，协同进化只发生在Amy编码区，而复制之间的差异进化发生在侧翼区。对重复基因座的5 '侧翼区的详细分析表明，两个旁系同源基因的翻译起始位点上游仅约450 bp具有序列相似性，表明祖先Amy基因的编码区与450 bp的5 ′-侧翼区一起作为一个单位复制。I元件是逆转子和控制I-元件之一。黑腹果蝇R杂种发育不全。为了研究I元件的进化，我们从黑腹果蝇种复合体中克隆了I元件并测定了其序列。毛里求斯杜氏果蝇、塞氏杜氏果蝇和拟杜氏果蝇的所有I元件与黑腹杜氏果蝇的染色体I元件的亲缘关系比与染色体中心I元件的亲缘关系更近。这些结果表明，缺陷的染色体中心I元件的黑腹果蝇的起源发生在物种分化和染色体I元件被淘汰之前。最近，染色体I元件在黑腹果蝇中重新侵入，可能是通过水平传递从拟果蝇引入的。

There are many duplicated genes including transposable slements, in the genome of higher organisms. In the present research project we mainly investigated molecular mechanisms of adaptive evolution in amylase system of Drosophila as well as evolution of a transposable element IFrom the uncleotide sequence data of duplicated Amy genes in 8 sibling species in the melanogaster species subgroup we found a strong within species similarity between the duplicated loci, in contrast to a strong similartty in the 5' and 3' flanking regions within each locus (proximal or distal) throughout the species subgroup. This result indicates that concerted evolution occurred only in the Amy coding region and that differentiated evolution between the duplication occurred in the flanking regions. The detailed analysis of the 5'-flanking regions of the duplicated loci showed that only about 450 bp immediately upstream to the translation intiation site of the two paralogous genes had sequence similarities, indicating that the coding region of the ancestral Amy gene duplicated together with 450 bp of the 5'-flanking region as one unit.I elements are one of the retroposon and control I-R hybrid dysgenesis in Drosophila melanogaster. To study the evolution of I elements, we cloned them from D.melanogaster species complex and determined the sequences. All I elements of D.mauritiana, D.sechellia and D.simulans are more closely related to the chromosomal I elements of D.melanogaster than to the chromocentral I elements. These findings demonstrate that the origin of the defective chromocentral I elements of D.melanogaster occurred before the time of species diverged and the chromosomal I elements were eliminated. The chromosomal I elements reinvaded in D.melanogaster recently, possibly introduced from D.simulans by horizontal transmission.