Reiji Okazaki

Reiji Okazaki (岡崎 令治 Okazaki Reiji, October 8, 1930 – August 1, 1975) was a pioneer Japanese molecular biologist, known for his research on DNA replication and especially for describing the role of Okazaki fragments which he discovered working with his wife Tsuneko.

Okazaki was born in Hiroshima, Japan. He graduated in 1953 from Nagoya University, and worked as a professor there after 1963. He died of leukemia (sequelae of Atomic bombings of Hiroshima) in 1975 at the age of 44; he had been heavily irradiated in Hiroshima when the first atomic bomb was dropped. His wife, Tsuneko, won the L'Oréal-UNESCO Awards for Women in Science in 2000 for her work.[1]

Okazaki Fragments

In 1968, Okazaki discovered the way in which the lagging strand of DNA is replicated via fragments, now called Okazaki fragments.[2][3][4][5]

The experiments by his group used E. coli. After introducing 3T-thymidine for only ten seconds to E. coli during DNA replication, he placed the sample in a test tube of alkaline sucrose. The larger, heavier DNA flowed to the bottom of the test tube, while the smaller, lighter DNA did not. When samples were taken from the bottom of the test tube, it was found that half were heavy and half were light, proving that half of the DNA was complete and half was in fragments. Then he took a sample of E. coli DNA that had been synthesized for an additional five seconds, and found all the activity now resulted in the larger molecular weight. Therefore, there were no longer any fragments. This proved that during the five second chase, the RNA primer was removed by DNA polymerase I, and the bases were joined together by DNA ligase, leaving the newly synthesized DNA fully mature and repaired.

References

  1. ↑ DNA researcher Okazaki wins int'l award for female scientists., the Free Library, 5 April 2015
  2. ↑ Okazaki, R.; Okazaki, T.; Sakabe, K.; Sugimoto, K.; Sugino, A. (1968). "Mechanism of DNA chain growth. I. Possible discontinuity and unusual secondary structure of newly synthesized chains". Proceedings of the National Academy of Sciences of the United States of America. 59 (2): 598–605. doi:10.1073/pnas.59.2.598. PMC 224714Freely accessible. PMID 4967086.
  3. ↑ Sugimoto, K.; Okazaki, T.; Okazaki, R. (1968). "Mechanism of DNA chain growth, II. Accumulation of newly synthesized short chains in E. Coli infected with ligase-defective T4 phages". Proceedings of the National Academy of Sciences of the United States of America. 60 (4): 1356–1362. doi:10.1073/pnas.60.4.1356. PMC 224926Freely accessible. PMID 4299945.
  4. ↑ Sugimoto, K.; Okazaki, T.; Imae, Y.; Okazaki, R. (1969). "Mechanism of DNA chain growth. 3. Equal annealing of T4 nascent short DNA chains with the separated complementary strands of the phage DNA". Proceedings of the National Academy of Sciences of the United States of America. 63 (4): 1343–1350. doi:10.1073/pnas.63.4.1343. PMC 223470Freely accessible. PMID 5260937.
  5. ↑ Okazaki, T.; Okazaki, R. (1969). "Mechanism of DNA chain growth. IV. Direction of synthesis of T4 short DNA chains as revealed by exonucleolytic degradation". Proceedings of the National Academy of Sciences of the United States of America. 64 (4): 1242–1248. doi:10.1073/pnas.64.4.1242. PMC 223275Freely accessible. PMID 4989398.


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