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{{Short description|Japanese molecular biologist (1930–1975)}}
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{{Short description|DNA Researcher; described the role of the Okazaki fragments}}{{nihongo|'''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]] along with his wife [[Tsuneko Okazaki|Tsuneko]].
{{Use dmy dates|date=February 2022}}
{{Infobox scientist
| native_name = 岡崎 令治
| name = Reiji Okazaki
| image =
| birth_name = Okazaki Reiji
| birth_date = {{birth date|1930|10|08}}
| birth_place = Hiroshima, Japan
| death_date = {{Death date and age|1975|08|01|1930|10|08}}
| death_place = Japan
| spouse = Tsuneko Okazaki
| partner =
| children =
| education = Nagoya University
| awards =
| fields = Molecular biology
| known_for = Okazaki Fragments
| workplaces = Nagoya University, Washington University, Stanford University
| thesis_title =
| thesis_url =
| thesis_year =
| doctoral_advisor =
| academic_advisors =
| doctoral_students =
}}
⚫
{{nihongo|'''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]] along with his wife [[Tsuneko Okazaki|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]] in 1975 at the age of 44; he had been heavily [[radiation|irradiated]] in [[Hiroshima]] when the [[Little Boy|first atomic bomb]] [[Atomic bombings of Hiroshima and Nagasaki|was dropped]].
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]] in Japan in 1975 at the age of 44 after traveling to the United States and Canada; he had been heavily [[radiation|irradiated]] in [[Hiroshima]] when the [[Little Boy|first atomic bomb]] [[Atomic bombings of Hiroshima and Nagasaki|was dropped]].<ref>{{Cite journal |last=Okazaki |first=Tsuneko |date=2017-05-11 |title=Days weaving the lagging strand synthesis of DNA — A personal recollection of the discovery of Okazaki fragments and studies on discontinuous replication mechanism |journal=Proceedings of the Japan Academy. Series B, Physical and Biological Sciences |volume=93 |issue=5 |pages=322–338 |doi=10.2183/pjab.93.020 |pmid=28496054 |pmc=5489436 |bibcode=2017PJAB...93..322O }}</ref>


== Okazaki Fragments ==
== Okazaki Fragments ==
In 1968, Okazaki discovered the way in which the lagging strand of DNA is replicated via fragments, now called [[Okazaki fragments]].<ref>{{Cite journal
In 1968, Reiji and [[Tsuneko Okazaki]] discovered the way in which the lagging strand of DNA is replicated via fragments, now called [[Okazaki fragments]].<ref>{{Cite journal
| last1 = Okazaki | first1 = R.
| last1 = Okazaki | first1 = R.
| last2 = Okazaki | first2 = T.
| last2 = Okazaki | first2 = T.
| last3 = Sakabe | first3 = K.
| last3 = Sakabe | first3 = K.
| last4 = Sugimoto | first4 = K.
| last4 = Sugimoto | first4 = K.
| last5 = Sugino | first5 = A.
| last5 = Sugino | first5 = A.
| title = Mechanism of DNA chain growth. I. Possible discontinuity and unusual secondary structure of newly synthesized chains
| title = Mechanism of DNA chain growth. I. Possible discontinuity and unusual secondary structure of newly synthesized chains
| journal = Proceedings of the National Academy of Sciences of the United States of America
| journal = Proceedings of the National Academy of Sciences of the United States of America
| volume = 59
| volume = 59
| issue = 2
| issue = 2
| pages = 598–605
| pages = 598–605
| year = 1968
| year = 1968
| pmid = 4967086
| pmid = 4967086
| pmc = 224714 | doi=10.1073/pnas.59.2.598
| pmc = 224714 | doi=10.1073/pnas.59.2.598
| bibcode = 1968PNAS...59..598O
| doi-access = free
| doi-access = free
⚫
}}</ref><ref>{{Cite journal
}}</ref><ref name=":0">{{Cite journal
| last1 = Sugimoto | first1 = K.
| last2 = Okazaki | first2 = T.
| last1 = Sugimoto | first1 = K.
| last3 = Okazaki | first3 = R.
| last2 = Okazaki | first2 = T.
⚫
| last3 = Okazaki | first3 = R.
| title = Mechanism of DNA chain growth, II. Accumulation of newly synthesized short chains in E. Coli infected with ligase-defective T4 phages
| title = Mechanism of DNA chain growth, II. Accumulation of newly synthesized short chains in E. Coli infected with ligase-defective T4 phages
| journal = Proceedings of the National Academy of Sciences of the United States of America
| journal = Proceedings of the National Academy of Sciences of the United States of America
| volume = 60
| issue = 4
| volume = 60
| pages = 1356–1362
| issue = 4
| pages = 1356–1362
| year = 1968
| year = 1968
| pmid = 4299945
| pmid = 4299945
| pmc = 224926
| pmc = 224926
| doi=10.1073/pnas.60.4.1356
| doi=10.1073/pnas.60.4.1356
| bibcode = 1968PNAS...60.1356S
| doi-access = free
| doi-access = free
⚫
}}</ref><ref>{{Cite journal
⚫
}}</ref><ref>{{Cite journal
| last1 = Sugimoto | first1 = K.
| last2 = Okazaki | first2 = T.
| last1 = Sugimoto | first1 = K.
| last3 = Imae | first3 = Y.
| last2 = Okazaki | first2 = T.
| last4 = Okazaki | first4 = R.
| last3 = Imae | first3 = Y.
| last4 = Okazaki | first4 = R.
| title = Mechanism of DNA chain growth. 3. Equal annealing of T4 nascent short DNA chains with the separated complementary strands of the phage DNA
| title = Mechanism of DNA chain growth. 3. Equal annealing of T4 nascent short DNA chains with the separated complementary strands of the phage DNA
| journal = Proceedings of the National Academy of Sciences of the United States of America
| journal = Proceedings of the National Academy of Sciences of the United States of America
| volume = 63
| issue = 4
| volume = 63
| pages = 1343–1350
| issue = 4
| pages = 1343–1350
| year = 1969
| year = 1969
| pmid = 5260937
| pmid = 5260937
| pmc = 223470 | doi=10.1073/pnas.63.4.1343
| pmc = 223470 | doi=10.1073/pnas.63.4.1343
| bibcode = 1969PNAS...63.1343S
| doi-access = free
| doi-access = free
}}</ref><ref>{{Cite journal
}}</ref><ref name=":1">{{Cite journal
⚫
| last1 = Okazaki | first1 = T.
| last2 = Okazaki | first2 = R.
| last1 = Okazaki | first1 = T.
| last2 = Okazaki | first2 = R.
| title = Mechanism of DNA chain growth. IV. Direction of synthesis of T4 short DNA chains as revealed by exonucleolytic degradation
| title = Mechanism of DNA chain growth. IV. Direction of synthesis of T4 short DNA chains as revealed by exonucleolytic degradation
| journal = Proceedings of the National Academy of Sciences of the United States of America
| journal = Proceedings of the National Academy of Sciences of the United States of America
| volume = 64
| issue = 4
| volume = 64
| pages = 1242–1248
| issue = 4
| pages = 1242–1248
| year = 1969
| year = 1969
| pmid = 4989398
| pmid = 4989398
| pmc = 223275
| pmc = 223275
| doi=10.1073/pnas.64.4.1242
| doi=10.1073/pnas.64.4.1242
| bibcode = 1969PNAS...64.1242O
| doi-access = free
| doi-access = free
}}</ref>
}}</ref>


{{Citation needed span|text=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 this five-second phase, 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.|date=March 2019|reason=}}
Their experiments used ''E. coli''. After introducing 3T-thymidine for only ten seconds to ''E. coli'' during DNA replication, they placed the sample in a test tube of alkaline sucrose.<ref name=":0" /> 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.<ref name=":1" /> This complete replacement of fragments was later identified as RNA primers being replaced with DNA nucleotides by [[DNA polymerase I]] and Okazaki fragments being joined by [[DNA ligase]].<ref>{{Cite web|title=11.2 DNA Replication - Microbiology {{!}} OpenStax|url=https://openstax.org/books/microbiology/pages/11-2-dna-replication|access-date=2021-10-02|website=openstax.org|date=November 2016 |language=en}}</ref>


==References==
==References==
{{Reflist}}
{{Reflist}}



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[[Category:1930 births]]
[[Category:1930 births]]
[[Category:1975 deaths]]
[[Category:1975 deaths]]
[[Category:Japanese biochemists]]
[[Category:20th-century Japanese biochemists]]
[[Category:Japanese molecular biologists]]
[[Category:Japanese molecular biologists]]
[[Category:People from Hiroshima]]
[[Category:Scientists from Hiroshima]]
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[[Category:Academic staff of Nagoya University]]
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[[Category:Nagoya University alumni]]
[[Category:Hibakusha]]
[[Category:Hibakusha]]
⚫
[[Category:Nagoya University faculty]]
⚫
[[Category:Nagoya University alumni]]




Latest revision as of 13:01, 6 September 2024

Reiji Okazaki
岡崎 令治
Born
Okazaki Reiji

(1930-10-08)October 8, 1930
Hiroshima, Japan
DiedAugust 1, 1975(1975-08-01) (aged 44)
Japan
EducationNagoya University
Known forOkazaki Fragments
SpouseTsuneko Okazaki
Scientific career
FieldsMolecular biology
InstitutionsNagoya University, Washington University, Stanford University

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 along 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 in Japan in 1975 at the age of 44 after traveling to the United States and Canada; he had been heavily irradiated in Hiroshima when the first atomic bomb was dropped.[1]

Okazaki Fragments

[edit]

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

Their experiments used E. coli. After introducing 3T-thymidine for only ten seconds to E. coli during DNA replication, they placed the sample in a test tube of alkaline sucrose.[3] 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.[5] This complete replacement of fragments was later identified as RNA primers being replaced with DNA nucleotides by DNA polymerase I and Okazaki fragments being joined by DNA ligase.[6]

References

[edit]
  1. ^ Okazaki, Tsuneko (11 May 2017). "Days weaving the lagging strand synthesis of DNA — A personal recollection of the discovery of Okazaki fragments and studies on discontinuous replication mechanism". Proceedings of the Japan Academy. Series B, Physical and Biological Sciences. 93 (5): 322–338. Bibcode:2017PJAB...93..322O. doi:10.2183/pjab.93.020. PMC 5489436. PMID 28496054.
  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. Bibcode:1968PNAS...59..598O. doi:10.1073/pnas.59.2.598. PMC 224714. PMID 4967086.
  3. ^ a b 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. Bibcode:1968PNAS...60.1356S. doi:10.1073/pnas.60.4.1356. PMC 224926. 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. Bibcode:1969PNAS...63.1343S. doi:10.1073/pnas.63.4.1343. PMC 223470. PMID 5260937.
  5. ^ a b 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. Bibcode:1969PNAS...64.1242O. doi:10.1073/pnas.64.4.1242. PMC 223275. PMID 4989398.
  6. ^ "11.2 DNA Replication - Microbiology | OpenStax". openstax.org. November 2016. Retrieved 2 October 2021.


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