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Tomoko Ohta

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Tomoko Ohta
太田 朋子, Ōta Tomoko
Tomoko Ohta
Born
原田 朋子, Harada Tomoko

(1933-09-07) 7 September 1933 (age 91)
Miyoshi, Japan
NationalityJapanese
Alma materNorth Carolina State University
University of Tokyo
Known forDevelopment of neutral theory of molecular evolution, and nearly neutral theory
SpouseYasuo Ohta (m.1960-1972)
AwardsJapan Academy Prize (1985)
Weldon Memorial Prize (1986)
Crafoord Prize (2015)
Japan's Order of Culture (2016)
Scientific career
FieldsEvolutionary biology
genetics
InstitutionsNational Institute of Genetics
North Carolina State University
Kihara Institute for Biological Research
Doctoral advisorKen-Ichi Kojima
Other academic advisorsMotoo Kimura
Hitoshi Kihara

Tomoko Ohta (太田 朋子, Ōta Tomoko, born Tomoko Harada 原田 朋子[1] 7 September 1933, Miyoshi, Aichi) is a Japanese scientist and Professor Emeritus of the National Institute of Genetics. Ohta works on population genetics/molecular evolution and is known for developing the nearly neutral theory of evolution.

Ohta has received many awards, including Japan's Order of Culture (2016). In 2015, Ohta and Richard Lewontin were jointly awarded the Crafoord Prize "for their pioneering analyses and fundamental contributions to the understanding of genetic polymorphism".[2][3]

Education

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Tomoko Ohta was born near Nagoya[4] and grew up in Miyoshi-cho in Aichi Prefecture.[5] She was in the 6th grade in elementary school when World War II ended. After the war, there were widespread changes in the social and educational systems, including the introduction of co-education. She attended junior high school in Toyota, and became interested in mathematics and physics. After senior high school, she entered Nagoya University. Having failed the examination for medical school, she transferred to the agriculture department at Tokyo University and majored in horticulture. Ohta graduated from the Agriculture Department of the University of Tokyo in 1956. After working at a publishing company, she was hired at the Kihara Institute for Biological Research. There she studied the cytogenetics of wheat and sugar beets.[4]

Hitoshi Kihara gave Ohta an opportunity to study abroad,[6] and in 1962, she entered the graduate program at North Carolina State University with support from a Fulbright scholarship.[7] Having initially planned to work on plant cytogenetics, she switched her focus to population genetics. She worked with her advisor, Ken-Ichi Kojima, on problems in stochastic population genetics,[6] Ohta completed her PhD in 1966.[6]

Career

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Returning to Japan in 1967, Ohta obtained a post-doctoral position at Japan’s National Institute of Genetics (NIG) under Motoo Kimura, then the only theoretical population geneticist in Japan.[6] Ohta was later promoted to a research position at the National Institute of Genetics where she remained from 1969 to 1996.[8] In April 1984, Ohta became a Full Professor in the Department of Population Genetics at NIG. She became Head of the Department of Population Genetics at NIG in 1988, and served as the Vice-Director of the National Institute of Genetics from 1989 to 1991.[7] Ohta served as Vice-President of the Society for the Study of Evolution in 1994.[9]

Research

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In the early 1960s, genetic theories about natural selection[8] assumed that inherited mutations were either harmful, and would be removed from the population, or beneficial, and would be transmitted to future individuals in the population. Based on this assumption, all individuals in a population were expected to be highly similar. However, in 1966, Richard Lewontin and John Lee Hubby found a much greater than expected amount of genetic variation among the individuals in a population. Motoo Kimura proposed a possible explanation, the neutral theory of evolution, to model changes in a population over time. According to his theory, some gene variants were neither advantageous nor harmful and were not affected by natural selection.[10]

Having worked on the neutral theory of evolution with Kimura, Ohta became convinced that division into good, neutral and harmful mutations was too simplistic a model to fully explain the observed data.[10] She theorized that neutral mutations (neither deleterious nor entirely neutral) still played an important role in evolution.[11][8] She first developed the slightly deleterious model of molecular evolution, and then a more general form, the nearly neutral theory of evolution.[12][13][14] Her theory challenged the position of her mentor Kimura, but they were able to debate fiercely and still maintain both their friendship and their independent positions.[15]

Ohta's theory of slightly deleterious fixations introduced a new class of origin-fixation models, with the goal of better explaining observed data.[12] While most of the mutations that affected encoded proteins were harmful, as long as they were not too significant ("nearly neutral"), they could remain in the population. Ohta also examined the role of chance and population size. She showed that population size is important in determining whether less-than-optimal variants can spread; in a smaller population, chance will have a greater effect on the set of outcomes, and natural selection will function more poorly. (In effect, rolling a small number of genetic dice is less likely to show a representative distribution of results than rolling a large number of dice.)[10] As a result, mutations that are slightly deleterious can become more easily fixed in small than in large populations, through genetic drift.[16] In 1974, Kimura and Ohto proposed a set of five general principles that might influence molecular evolution.[10]

When Ohta first published her Nearly Neutral theory, she faced difficulty in attracting the scientific research community's attention and acceptance.[8] Supporting data in protein evolution was sequentially collected in the 1990s, with even more evidence supporting her theory made available throughout the 21st century. There is more and more evidence evolving that supports her nearly neutral theory of evolution.[17][10][6]

"The nearly neutral theory in its initial form may not explain all aspects of polymorphisms but, almost 50 years after it was first proposed by Tomoko Ohta (Ohta 1973), it still constitutes an excellent starting point for further theoretical developments."[17]

Recognition

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Ohta’s work in the field of molecular evolution has been recognized internationally.

Bibliography (Works in English)

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Books

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  • Kimura, Motoo; Ohta, Tomoko (1971). Theoretical aspects of population genetics. Princeton, NJ: Princeton Univ. Press. ISBN 9780691080987.
  • Ōta, Tomoko (1980). Evolution and variation of multigene families. Berlin: Springer-Verlag. ISBN 978-3-540-09998-7.
  • Ohta, Tomoko; Aoki, Kenichi, eds. (1985). Population genetics and molecular evolution: papers marking the sixtieth birthday of Motoo Kimura. Tokyo: Japan Scientific Societies Press. ISBN 978-0387155845.

Papers

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References

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  1. ^ a b Jones, Colin P.A. (9 November 2016). "So-called egalitarian Japan is still honor-bound". Special To The Japan Times.
  2. ^ a b "The Crafoord Prize in Biosciences 2015". Crafoord Prize. 14 January 2015. Retrieved 28 February 2023.
  3. ^ Söderström, Bo (April 2015). "Discovery of genetic polymorphism: Richard Lewontin and Tomoko Ohta awarded the Crafoord Prize in Biosciences 2015" (PDF). Ambio. 44 (3): 165. doi:10.1007/s13280-015-0640-1. PMC 4357622. PMID 25712534. Retrieved 28 February 2023.
  4. ^ a b Sridhar, Hari; Ohta, Tomoko (22 November 2020). "Revisiting Ohta 1973". Reflections on Papers Past.
  5. ^ DeBakcsy, Dale (27 May 2020). "Breaking Neutral: The Population Genetics Of Tomoko Ohta". Women You Should Know®. Retrieved 28 February 2023.
  6. ^ a b c d e Ohta, Tomoko (2012), "Tomoko Ohta" (PDF), Current Biology, 22 (16): R618–R619, doi:10.1016/j.cub.2012.06.031, PMID 23082325
  7. ^ a b c "Profile of Tomoko Ohta". Perspectives on Molecular Evolution.
  8. ^ a b c d Sato, Narumi. "National Institute of Genetics: OHTA, Tomoko - Professor Emeritus". National Institute of Genetics. Retrieved 20 April 2016.
  9. ^ "Officers and Editors" (PDF). Society for the Study of Evolution Past. Retrieved 28 February 2023.
  10. ^ a b c d e "The Crafoord Prize in Biosciences 2015" (PDF). The Royal Swedish Academy of Sciences. Retrieved 28 February 2023.
  11. ^ Ruse, Michael; Travis, Joseph (1 January 2009). Evolution: The First Four Billion Years. Harvard University Press. ISBN 978-0-674-06221-4.
  12. ^ a b McCandlish, David M.; Stoltzfus, Arlin; Dykhuizen, Daniel E. (2014). "Modeling Evolution Using the Probability of Fixation: History and Implications". The Quarterly Review of Biology. 89 (3): 225–252. doi:10.1086/677571. ISSN 0033-5770. JSTOR 10.1086/677571. PMID 25195318. S2CID 19619966. Retrieved 28 February 2023.
  13. ^ Razeto-Barry, Pablo; Díaz, Javier; Vásquez, Rodrigo A. (2012). "The Nearly Neutral and Selection Theories of Molecular Evolution Under the Fisher Geometrical Framework: Substitution Rate, Population Size, and Complexity". Genetics. 191 (2): 523–534. doi:10.1534/genetics.112.138628. ISSN 0016-6731. PMC 3374315. PMID 22426879.
  14. ^ Steen, TY (29 November 2008). "The Case of Ohta Tomoko: A Woman Geneticist in the Neutralist-Selectionist Evolution Controversy". Historia Scientiarum. Second Series. 18 (2): 172–184.
  15. ^ Steen, TY. (1996). "Always an excentric?: A Brief Biography of Motoo Kimura". Journal of Genetics. 75 (1): 19–25. doi:10.1007/BF02931748. S2CID 29545568.
  16. ^ Nei, Masatoshi; Suzuki, Yoshiyuki; Nozawa, Masafumi (22 September 2010). "The Neutral Theory of Molecular Evolution in the Genomic Era". Annual Review of Genomics and Human Genetics. 11: 265–289. doi:10.1146/annurev-genom-082908-150129. PMID 20565254. Retrieved 28 February 2023.
  17. ^ a b Chen, Jun; Glémin, Sylvain; Lascoux, Martin (April 2020). "From Drift to Draft: How Much Do Beneficial Mutations Actually Contribute to Predictions of Ohta's Slightly Deleterious Model of Molecular Evolution?". Genetics. 214 (4): 1005–1018. doi:10.1534/genetics.119.302869. ISSN 1943-2631. PMC 7153929. PMID 32015019.
  18. ^ "Tomoko Ohta". American Academy of Arts & Sciences. Retrieved 28 February 2023.
  19. ^ "The Imperial Prize, Japan Academy Prize, Duke of Edinburgh Prize Recipients 71st - 80th | The Japan Academy". www.japan-acad.go.jp. Retrieved 28 February 2023.
  20. ^ a b Yount, Lisa (2007). A to Z of Women in Science and Math. Infobase Publishing. pp. 232–233. ISBN 978-1-4381-0795-0.
  21. ^ "Tomoko Ohta". National Academy of Sciences. Retrieved 28 February 2023.
  22. ^ "Emperor to present two awards to Tanaka". The Japan Times. 31 October 2002. Retrieved 28 February 2023.
  23. ^ "SMBE Lifetime Contribution Award". Society for Molecular Biology & Evolution.
  24. ^ Slatkin, Montgomery (2008). "Linkage disequilibrium — understanding the evolutionary past and mapping the medical future". Nature Reviews. Genetics. 9 (6): 477–485. doi:10.1038/nrg2361. ISSN 1471-0056. PMC 5124487. PMID 18427557.
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