Molecular population genetical studies of evolution.

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Recent progress in molecular biology has brought a large impact on the study of evolution. In the present project, we investigated the amount of polymorphisms and structures and changes of genes at the molecular level using Drosophila (Yamazaki,Tobari,Ishiwa,Kusakabe and Takano) and wild plants (Miyashita) as model organisms. These studies have revealed various aspects of molecular evolution. As many previous studies had shown, most molecular data are compatible with the neutral theory of molecular evolution proposed by Kimura in 1968 which states that most gene substitutions at the molecular level are due to random fixations of selectively neutral mutations. However, by selecting genes, period (behavior) and amylase (inducible), which are directly involved in organismal response to the environments, we obtained experimental evidences of adaptive amino acid substitutions especially during speciation. Also Hiroyoshi found interesting phenomena in his study on sex determination factors i … More n house flies and now molecular approaches to clarify this phenomena are in progress. Harada estimated the spontaneous mutation rate of isozyme loci, which is a very important parameter in the study of evolution, to be 7 x 10^<-7> per generation.As to theoretical studies, much progress was made in the development of the neutral theory (Kimura,Ohta,Tajima,Tachida and Iizuka), the methodology of constructing phylogeny (Tajima), evolutionary theories of multigene families and repeated sequences (Ohta and Tachida) and studies on the maintenance mechanisms of polymorphisms (Takahata). In our project, we attempted to understand the molecular mechanisms of adaptive evolution combining theoretical and experimental approaches. Our findings are considered to be landmarks to this new area of molecular evolution which investigates the interrelationships between the phenotypic evolution and the molecular evolution. We now believe that the unified understanding of evolution at both (molecular and phenotypic) levels is within our reach. Less