Molecular Population Genetics of Duplicated Genes in Drosophila.

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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.