Tomoko Ohta

National Institute of Genetics


Election Year: 2002
Primary Section: 27, Evolutionary Biology
Secondary Section: 26, Genetics
Membership Type: Foreign Associate

Research Interests

My major research topic is to develop the nearly neutral theory of molecular evolution. The theory contends that interaction of random genetic drift and natural selection is important for evolution of genes and genetic systems, and emphasis has been on the role of slightly deleterious mutations. Population genetics studies have been combined with DNA sequence analyses. In particular, comparative studies of mammalian genes have revealed the prevalence of slightly deleterious amino acid substitutions. To account for interaction systems at various levels the nearly neutral theory has been extended to incorporate slightly advantageous mutations that include compensatory changes. My next topic is the evolution of gene families. A population genetics model for gene family evolution has been developed that incorporates unequal crossing over and gene conversion. Here again both drift and selection are working. It has been shown that in gene families with uniform members like those of ribosomal RNA or histone, the rate of unequal crossing over or gene conversion is high and concerted evolution takes place. For gene families with variable members their rates are expected to be low; however, gene conversion followed by natural selection may contribute to high variability of some gene families.

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