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Portrait of Marshall W. Nirenberg
Photo: Hecht, Gerald V. (National Institutes of Health)., http://profiles.nlm.nih.gov/JJ/B/B/B/T/_/jjbbbt_.jpg. The image is cropped by Ekamaloff · Public domain via Wikimedia Commons

Nobel Prize in Physiology or Medicine · 1968

Marshall W. Nirenberg

With a colleague, he read the first word of the genetic code, showing how cells turn the letters of their genes into proteins.

The Nobel citation: “for their interpretation of the genetic code and its function in protein synthesis”
Born
April 10, 1927, New York, NY, USA
Died
January 15, 2010, New York, NY, USA
Shared with
Robert W. Holley, H. Gobind Khorana
Affiliation at the time
National Institutes of Health, USA

Medicine prize

1968

Shared with 2 other laureates.

Age that year

41years

Born in 1927.

Headline credited impact

4,350–44,500lives saved

Deaths averted by mRNA COVID-19 vaccines, credited to deciphering the genetic code. How it was built

Sources cited

40

Fact-checked September 24, 2026.

  • In the early hours of Saturday, 27 May 1961, his partner Heinrich Matthaei ran the test that read the first word of the genetic code: UUU means phenylalanine.
  • He came to the code as an outsider: a biochemist whose only genetics schooling was evening classes. At least one colleague thought the project would wreck his career.
  • He was the first scientist from NIH's own labs to win a Nobel Prize. Many NIH colleagues set aside their work to help his lab race a larger team in New York.
  • In 1967 he predicted that cells would be programmed with man-made genetic messages within 25 years, and argued that an informed society must decide how to use that power.
  • At a 1961 congress in Moscow his first talk drew about 30 people. Francis Crick arranged for him to give it again, this time to about a thousand.

The breakthrough

Cracking the genetic code, from UUU to all 64 codons (1961-1966)

Every cell stores its instructions in DNA, written with just four chemical letters. Proteins, the molecules that do most of the work in our bodies, are chains built from 20 kinds of amino acids. By 1960 scientists suspected that RNA copies of genes carried these instructions to the cell's protein factories, but nobody knew how a four-letter alphabet could spell out a 20-letter one. Nirenberg and his postdoctoral partner Heinrich Matthaei ground up E. coli bacteria and kept the liquid inside, which can still build proteins in a test tube. Then they gave it an artificial RNA made of one letter, U, repeated over and over. Imagine feeding a translating machine a page that says only 'U U U U' and watching it print the same word again and again. The machine made a protein built only from phenylalanine, so UUU was the code word for phenylalanine. Over the next five years, Nirenberg's team, Severo Ochoa's larger rival lab in New York and H. Gobind Khorana's lab in Wisconsin worked out the rest. In 1964 he and Philip Leder found that an RNA just three letters long was enough to make the transfer RNA carrying the matching amino acid stick to the ribosome, the protein factory. That let them read the order of the letters in each word. By 1966 the 64-word dictionary was essentially complete. His lab also showed that bacteria, amphibians and mammals read the code almost identically.[1],[3],[4],[6],[7],[11],[16],[17],[31]

“decisions concerning the application of this knowledge must ultimately be made by society, and only an informed society can make such decisions wisely.”
Marshall W. Nirenberg, From his editorial 'Will Society Be Prepared?' in Science, 11 August 1967, adapted from remarks accepting a 1966 award, on who should decide how the power to program cells is used.[15]

What it meant for humanity

The genetic code is the dictionary every living thing uses to turn genes into proteins. Once it was known, scientists could read a gene and predict the protein it makes, or write a gene to get the protein they wanted. The Nobel committee member who presented the 1968 prize said the work opened a path to understanding the many diseases in which heredity plays a part. Sickle cell disease is a clear case: one change in the hemoglobin gene swaps a single amino acid, and that swap bends red blood cells into sickles. The code also made genetic engineering practical. In 1977 scientists built a gene for the hormone somatostatin from scratch and had bacteria make the hormone, and in 1979 they did the same for the two chains of human insulin. NIH's history office credits his work with laying the groundwork for research as varied as gene therapy, the cloning of Dolly the sheep and the Human Genome Project. A recent example is the mRNA vaccines against COVID-19, approved in December 2020. Each is a made-to-order RNA message, written in the code's four letters (one of them chemically tweaked), that tells our cells to build one virus protein so the immune system learns to recognize it. That is close to what Nirenberg forecast in 1967, when he wrote that man-made genetic messages would one day program cells. COVID-19 vaccines of all kinds averted more than 2.5 million deaths by October 2024 in one cautious study, and 14 to 20 million in their first year alone in another; mRNA vaccines made up roughly 5 billion of about 13.5 billion doses. Nirenberg's work was one early link in the long chain behind these uses.

  • In the May 1961 run, the tube with radioactive phenylalanine showed about 38,000 counts per milligram of protein, against a background of about 70 in the control tubes: UUU meant phenylalanine.[11]
  • The Nobel presenter noted that within five years of Nirenberg's first report, in August 1961, the whole code had been worked out, chiefly by his lab and Khorana's.[4],[7]
  • His lab found that transfer RNAs from bacteria, amphibians and mammals read code words almost identically, evidence that nearly all life shares one genetic language.[3],[12],[15]
  • Knowing the code lets doctors read what a gene change does to its protein. The sickle cell variant in the hemoglobin gene swaps a single amino acid, and that one swap bends red blood cells into sickles.[4],[30]
  • In 1977 and 1979 bacteria made somatostatin and human insulin chains from genes built from scratch, the kind of cell programming Nirenberg had forecast in 1967.[15],[28],[29]
  • The mRNA COVID-19 vaccines, synthetic messages written in the code's letters, were approved in December 2020. All COVID-19 vaccines together averted more than 2.5 million deaths by October 2024.[32],[34]

Impact in numbers

The genetic code is one of the central facts of biology, and most of its value cannot honestly be counted. Reading any gene for the protein it makes, spotting the gene changes behind inherited diseases, and making human proteins in bacteria all depend on it. We therefore make one small numeric claim. The mRNA COVID-19 vaccines are synthetic genetic messages that our cells translate with the code, a clear and measurable descendant of Nirenberg's 1961 proof that a man-made RNA can direct protein building. We credit him with half of one percent of the lives they saved, because the result also needed Matthaei, Khorana, Holley and other code-breakers, the discovery of messenger RNA, decades of RNA chemistry, Karikó and Weissman's modified bases, fatty delivery bubbles and the vaccine makers. The same half percent of the vaccines' rare heart-inflammation cases is counted against him. His early public warnings about the ethics of rewriting cells are part of his legacy too.

Fundamental scienceHealth

Each number is the laureate’s credited share of a real-world outcome, cumulative to 2025. The whole outcome, the share of credit, and the reasoning are shown so you can check the arithmetic. Outcomes shared with other laureates are counted once on the impact page.

  • Low confidenceRippleModeledHealth

    Deaths averted by mRNA COVID-19 vaccines, credited to deciphering the genetic code

    4,350–44,500

    lives saved, credited share

    That is 0.5% of 870,000–8.9 million lives saved since 2020.

    How this number was built

    Range reused from the shared mrna-vaccines outcome. All COVID-19 vaccines: 2.5M deaths averted to Oct 2024 (Ioannidis 2025; 1 per 5,400 doses, so ~13.5B doses) to 19.8M in year one (Watson 2022, excess deaths). mRNA doses: Pfizer-BioNTech 4.3B by Mar 2023 + Moderna 0.81B in 2021 = ~5.1B (~38%). Low 2.5M x 35% = 0.87M; high 19.8M x 45% = 8.9M. Share 0.005: the vaccines are synthetic mRNAs whose coding sequence is written (and codon-optimized) with the codon table Nirenberg's lab helped decipher, and his 1961 poly-U test first showed a man-made RNA directing protein synthesis. But the code was shared work (Matthaei, Khorana, Holley, Ochoa's group, Leder, Crick and Brenner), mRNA was discovered by others, and the vaccines also needed in vitro transcription, modified bases (Kariko and Weissman, 0.3), lipid nanoparticles and a stabilized spike. His slice: 4,350-44,500 lives.[1],[16],[32],[33],[34],[35],[36],[37]

    Sources: JAMA Health Forum (PubMed record); The Lancet Infectious Diseases (PubMed record); Pfizer Inc.; U.S. Securities and Exchange Commission (EDGAR); The Nobel Assembly at Karolinska Institutet (NobelPrize.org); The Nobel Committee for Physiology or Medicine (NobelPrize.org); NobelPrize.org (Nobel Prize Outreach); Proceedings of the National Academy of Sciences (via PubMed Central)

  • HarmLow confidenceRippleModeledHealth

    Myocarditis cases linked to mRNA COVID-19 vaccines, credited to deciphering the genetic code

    100–350

    people harmed, credited share

    That is 0.5% of 20,000–70,000 people harmed since 2020.

    How this number was built

    Range reused from the shared mrna-vaccine-myocarditis outcome. Oster et al. (2022): 1,626 confirmed cases after 354.1M US mRNA doses = 0.46 per 100,000 doses (passive reporting, likely an undercount). Mevorach et al. (2021), Israeli active surveillance: 136 definite or probable cases among about 5.1M two-dose recipients (at least 10.2M doses) = about 1.3 per 100,000 doses. Applied to about 5.1B mRNA doses (Pfizer-BioNTech 4.3B + Moderna 0.81B): 23,000, rounded down to 20,000, to 66,000, rounded up to 70,000. In Israel 95% of cases were mild; one was fatal. Share 0.005, matching the benefit claim: about 100-350 cases.[36],[37],[38],[39]

    Sources: JAMA (PubMed record); New England Journal of Medicine (PubMed record); Pfizer Inc.; U.S. Securities and Exchange Commission (EDGAR)

The double edge

No direct harm has been traced to Nirenberg's own experiments, but the knowledge they unlocked cuts both ways, and he said so himself. In 1961 the Nobel chemist Arne Tiselius warned that reading the code could lead to tampering with life and creating new diseases. In his 1967 Science editorial, Nirenberg warned that people might learn to program their own cells long before they understood the consequences, and urged restraint until society could decide wisely. Joshua Lederberg replied that such warnings could breed public misunderstanding and heavy-handed control of research. Technologies built on the code do carry real risks. The mRNA COVID-19 vaccines, for example, can cause rare heart inflammation (myocarditis), mostly in young men, and we count a small slice of those cases against him at the same share as the benefit. A last caveat concerns credit: his partner Heinrich Matthaei ran the decisive 1961 experiment, but a Nobel Prize can be shared by at most three people, and Matthaei was not among the 1968 winners.

  • Moderate

    The power to rewrite life

    Knowing the code let scientists write genetic instructions, not just read them. In 1961 Arne Tiselius warned this could lead to tampering with life and new diseases. Nirenberg's 1967 editorial urged that people not instruct their own cells until they had the wisdom to do so; Joshua Lederberg answered that such caution could invite public misunderstanding and bureaucratic policing of research.[8],[9],[15]

  • Minor

    Rare heart inflammation after mRNA vaccines

    mRNA COVID-19 vaccines, a late descendant of the code, can cause myocarditis, mostly in young males after a second dose. In US reports, 1,626 cases met the case definition after 354 million doses. In Israel, 95% of 136 definite or probable cases were mild, but one was fatal.[38],[39]

  • Minor

    Credit for the first code word

    NobelPrize.org credits the poly-U experiment to Nirenberg and Heinrich Matthaei, and it was Matthaei who ran the decisive test in May 1961. Nobel rules let at most three people share a prize, and the 1968 prize went to Nirenberg, Robert Holley and H. Gobind Khorana.[1],[11],[27]

Against the odds

Nirenberg did not face persecution himself, and his story is mostly one of American opportunity. But he grew up in a country where, according to the US Holocaust Memorial Museum, antisemitism was common and grew through the 1930s, and where 1924 immigration laws favored northern and western Europeans over the eastern Europeans among whom most of Europe's Jews lived. Starting in the 1920s, most American medical schools capped the number of Jewish students; the caps held firm through World War II and disappeared only around 1970. Yale's medical school, for one, set a limit of five Jewish students per class. Nirenberg's own hurdles were of a different kind. As a boy he developed rheumatic fever, and his family left New York for the warmer climate of Orlando, Florida. He then came to the genetic code as an outsider: a biochemist whose only genetics schooling was a set of evening classes at NIH. Several colleagues considered the attempt naive, and one thought it could end his career. Once he succeeded, his government lab found itself racing the larger, well-funded team of the Nobel laureate Severo Ochoa. Later he used his fame to press the Soviet Union to free the imprisoned Soviet Jewish scientist Mikhail Shtern.

  • —

    Quota

    Starting in the 1920s, most US medical schools capped Jewish admissions. The caps were still firmly in place in 1945 and had disappeared by around 1970. Yale's medical school, for one, allowed at most five Jewish students per class.[25],[26]

  • —

    Discrimination

    Antisemitism was common in the United States and grew through the 1930s, while the 1924 immigration laws favored northern and western Europeans over the eastern Europeans among whom most of Europe's Jews lived.[24]

  • 1941

    Other

    As a boy he developed rheumatic fever, and the family moved from New York to Orlando, Florida, for its warmer weather.[2],[5]

  • 1959

    Other

    He tackled the genetic code as a biochemist whose genetics background was a few evening classes at NIH. Several colleagues considered the attempt naive; one thought it could end his career.[6]

Jewish background

Both parents JewishCulturally Jewish

Nirenberg was born in New York City to a Jewish family, the son of Harry Nirenberg and Minerva Bykowsky Nirenberg. The Encyclopaedia Judaica gives him an entry, and the Jewish Virtual Library lists him as a Jewish American scientist. We found no record of religious practice. His papers at the National Library of Medicine show Jewish ties in public life: in 1975 he wrote to the Soviet head of state asking him to free the jailed Soviet Jewish scientist Mikhail Shtern; in 1978 Israel's Weizmann Institute gave him an honorary doctorate; and in the 1980s a project on Jewish life in Florida asked to feature him as a role model for Jewish young people.[5],[18],[19],[20],[21],[22],[23],[40]

Key dates

  1. April 10, 1927

    Born in New York City to Harry and Minerva Nirenberg.[1],[2]

  2. 1939

    After a bout of rheumatic fever, moves with his family to Orlando, Florida, for its warm climate (the Nobel biography says 1939; NIH's library says 1941).[2],[5],[10]

  3. 1948

    Earns a BS at the University of Florida, followed in 1952 by an MS in zoology with a thesis on caddis flies.[2],[5]

  4. 1957

    Earns a PhD in biological chemistry at the University of Michigan and joins the National Institutes of Health as a postdoctoral fellow.[2],[5]

  5. May 27, 1961

    With Heinrich Matthaei, shows that an artificial RNA made only of U directs the building of a protein made only of phenylalanine: the first word of the genetic code.[1],[11],[16]

  6. July 1961

    Marries Perola Zaltzman, a Brazilian-trained chemist who became an NIH biochemist.[2],[10]

  7. August 1961

    Presents the poly-U result at the International Congress of Biochemistry in Moscow, first to about 30 people, then to about a thousand.[6],[11]

  8. 1964

    With Philip Leder, shows that three-letter RNA pieces make the matching amino-acid-carrying transfer RNA stick to ribosomes, a fast way to read each code word's letter order.[3],[17]

  9. 1966

    Announces that the code words for all 20 amino acids have been deciphered.[7],[10]

  10. August 11, 1967

    Publishes 'Will Society Be Prepared?' in Science, warning that people may learn to program cells before they can judge the consequences.[9],[14],[15]

  11. 1968

    Shares the Nobel Prize in Physiology or Medicine with Robert W. Holley and H. Gobind Khorana for interpreting the genetic code; the first NIH intramural scientist to win.[1],[4],[13]

  12. 1978

    Receives an honorary doctorate from the Weizmann Institute of Science in Israel.[23]

  13. December 23, 2005

    Four years after Perola's death, marries Myrna Weissman, a professor of epidemiology and psychiatry at Columbia University.[5],[10]

  14. January 15, 2010

    Dies of cancer at his home in New York, aged 82.[1],[5],[10]

Sources

  1. 1.Marshall W. Nirenberg - Facts · NobelPrize.org (Nobel Prize Outreach)
  2. 2.Marshall W. Nirenberg - Biographical · NobelPrize.org (from Les Prix Nobel en 1968, Nobel Foundation, 1969), 1969
  3. 3.The Genetic Code (Nobel Lecture, 12 December 1968) · NobelPrize.org, 1968
  4. 4.Award ceremony speech, Nobel Prize in Physiology or Medicine 1968 (presentation by Professor P. Reichard) · NobelPrize.org, 1968
  5. 5.Biographical Overview, The Marshall W. Nirenberg Papers (Profiles in Science) · U.S. National Library of Medicine
  6. 6.Synthetic RNA and the Poly-U Experiments, 1959-1962 (Profiles in Science) · U.S. National Library of Medicine
  7. 7.Translating the Code of Life and the Nobel Prize, 1962-1968 (Profiles in Science) · U.S. National Library of Medicine
  8. 8.Public Reactions to the Genetic Code, 1961-1968 (Profiles in Science) · U.S. National Library of Medicine
  9. 9.Beyond the Laboratory: Professional, Personal, and Political Life, 1967-2002 (Profiles in Science) · U.S. National Library of Medicine
  10. 10.Brief Chronology, The Marshall W. Nirenberg Papers (Profiles in Science) · U.S. National Library of Medicine
  11. 11.Marshall Nirenberg: Deciphering the Genetic Code - The Poly-U Experiment (archived exhibit page) · Office of NIH History (via Internet Archive), 2004
  12. 12.Marshall Nirenberg: Deciphering the Genetic Code - Universality (archived exhibit page) · Office of NIH History (via Internet Archive), 2004
  13. 13.Marshall Nirenberg: Deciphering the Genetic Code - Nobel Prize (archived exhibit page) · Office of NIH History (via Internet Archive), 2004
  14. 14.Marshall Nirenberg: Deciphering the Genetic Code - Will Society be Prepared? (archived exhibit page) · Office of NIH History (via Internet Archive), 2005
  15. 15.Will Society Be Prepared? (Nirenberg MW, editorial, Science 157:633, 11 August 1967), copy in the Nirenberg Papers · U.S. National Library of Medicine, Profiles in Science, 1967
  16. 16.The dependence of cell-free protein synthesis in E. coli upon naturally occurring or synthetic polyribonucleotides (Nirenberg MW, Matthaei JH, PNAS 47:1588-1602) · Proceedings of the National Academy of Sciences (via PubMed Central), 1961
  17. 17.RNA codewords and protein synthesis: the effect of trinucleotides upon the binding of sRNA to ribosomes (Nirenberg M, Leder P, Science 145:1399-1407) · Science (PubMed record), 1964
  18. 18.Marshall Warren Nirenberg · Wikipedia
  19. 19.Marshall Nirenberg · Jewish Virtual Library (American-Israeli Cooperative Enterprise)
  20. 20.Letter from Marcia Kerstein Zerivitz to Marshall W. Nirenberg (MOSAIC: Jewish Life in Florida project) · U.S. National Library of Medicine, Profiles in Science, 1988
  21. 21.Letter from Lilli S. Chertoff, Committee of Concerned Scientists, to Marshall W. Nirenberg (on Mikhail Shtern) · U.S. National Library of Medicine, Profiles in Science, 1975
  22. 22.Letter from Marshall W. Nirenberg to Nikolai V. Podgorny · U.S. National Library of Medicine, Profiles in Science, 1975
  23. 23.Letter from David Moushine, Weizmann Institute of Science, to Marshall W. Nirenberg (honorary doctorate) · U.S. National Library of Medicine, Profiles in Science, 1978
  24. 24.How did the United States government and American people respond to Nazism? · United States Holocaust Memorial Museum, Holocaust Encyclopedia
  25. 25.Jewish American Heritage Month: The Forgotten History of Quotas in American Medical School Admissions · Himmelfarb Health Sciences Library, George Washington University, 2023
  26. 26.Why Did the United States Medical School Admissions Quota for Jews End? (Halperin EC) · The American Journal of the Medical Sciences (PubMed record), 2019
  27. 27.Statutes of the Nobel Foundation · NobelPrize.org
  28. 28.Expression in Escherichia coli of a chemically synthesized gene for the hormone somatostatin (Itakura K et al.) · Science (PubMed record), 1977
  29. 29.Expression in Escherichia coli of chemically synthesized genes for human insulin (Goeddel DV et al., PNAS 76:106-110) · Proceedings of the National Academy of Sciences (via PubMed Central), 1979
  30. 30.HBB gene (hemoglobin subunit beta) · MedlinePlus Genetics, U.S. National Library of Medicine
  31. 31.How do genes direct the production of proteins? · MedlinePlus Genetics, U.S. National Library of Medicine
  32. 32.Press release: The Nobel Prize in Physiology or Medicine 2023 · The Nobel Assembly at Karolinska Institutet (NobelPrize.org), 2023
  33. 33.Scientific background 2023: Discoveries concerning nucleoside base modifications that enabled the development of effective mRNA vaccines against COVID-19 · The Nobel Committee for Physiology or Medicine (NobelPrize.org), 2023
  34. 34.Global Estimates of Lives and Life-Years Saved by COVID-19 Vaccination During 2020-2024 (Ioannidis JPA et al.) · JAMA Health Forum (PubMed record), 2025
  35. 35.Global impact of the first year of COVID-19 vaccination: a mathematical modelling study (Watson OJ et al.) · The Lancet Infectious Diseases (PubMed record), 2022
  36. 36.Pfizer-BioNTech COVID-19 Vaccine: U.S. Manufacturing and Distribution Fact Sheet (March 2023) · Pfizer Inc., 2023
  37. 37.Moderna, Inc. Form 8-K (January 2022): 2021 COVID-19 vaccine deliveries · U.S. Securities and Exchange Commission (EDGAR), 2022
  38. 38.Myocarditis Cases Reported After mRNA-Based COVID-19 Vaccination in the US From December 2020 to August 2021 (Oster ME et al.) · JAMA (PubMed record), 2022
  39. 39.Myocarditis after BNT162b2 mRNA Vaccine against Covid-19 in Israel (Mevorach D et al.) · New England Journal of Medicine (PubMed record), 2021
  40. 40.Nirenberg, Marshall Warren (Encyclopaedia Judaica, 2nd ed., entry by Michael Denman) · Encyclopaedia Judaica (Gale / Macmillan Reference USA), via Encyclopedia.com, 2007

Fact-checked on September 24, 2026 by a separate AI fact-checking pass that re-opened the sources, with 10 corrections made. How we check

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