Genetic code: Difference between revisions

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This was followed by experiments in [[Severo Ochoa]]'s laboratory that demonstrated that the poly-[[adenine]] RNA sequence (AAAAA...) coded for the polypeptide poly-[[lysine]]<ref name="pmid13946552">{{cite journal | vauthors = Gardner RS, Wahba AJ, Basilio C, Miller RS, Lengyel P, Speyer JF | title = Synthetic polynucleotides and the amino acid code. VII | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 48 | issue = 12 | pages = 2087–94 | date = Dec 1962 | pmid = 13946552 | pmc = 221128 | doi = 10.1073/pnas.48.12.2087 | bibcode = 1962PNAS...48.2087G | doi-access = free }}</ref> and that the poly-[[cytosine]] RNA sequence (CCCCC...) coded for the polypeptide poly-[[proline]].<ref name="pmid13998282">{{cite journal | vauthors = Wahba AJ, Gardner RS, Basilio C, Miller RS, Speyer JF, Lengyel P | title = Synthetic polynucleotides and the amino acid code. VIII | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 49 | issue = 1 | pages = 116–22 | date = Jan 1963 | pmid = 13998282 | pmc = 300638 | doi = 10.1073/pnas.49.1.116 | bibcode = 1963PNAS...49..116W | doi-access = free }}</ref> Therefore, the codon AAA specified the amino acid [[lysine]], and the codon CCC specified the amino acid [[proline]]. Using various [[copolymers]] most of the remaining codons were then determined.

Subsequent work by [[Har Gobind Khorana]] didentified the rest of the genetic code. Shortly thereafter, [[Robert W. Holley]] determined the structure of [[transfer RNA]] (tRNA), the adapter molecule that facilitates the process of translating RNA into protein. This work was based upon Ochoa's earlier studies, yielding the latter the [[Nobel Prize in Physiology or Medicine]] in 1959 for work on the [[enzymology]] of RNA synthesis.<ref name="Nobel_1959">{{cite press release |url=http://nobelprize.org/nobel_prizes/medicine/laureates/1959/index.html |title=The Nobel Prize in Physiology or Medicine 1959 |quote=The Nobel Prize in Physiology or Medicine 1959 was awarded jointly to Severo Ochoa and Arthur Kornberg 'for their discovery of the mechanisms in the biological synthesis of ribonucleic acid and deoxyribonucleic acid'. |publisher=The Royal Swedish Academy of Science |date=1959 |access-date=2010-02-27}}</ref>

Extending this work, Nirenberg and [[Philip Leder]] revealed the code's triplet nature and deciphered its codons. In these experiments, various combinations of [[mRNA]] were passed through a filter that contained [[ribosome]]s, the components of cells that [[Translation (biology)|translate]] RNA into protein. Unique triplets promoted the binding of specific tRNAs to the ribosome. Leder and Nirenberg were able to determine the sequences of 54 out of 64 codons in their experiments.<ref name="pmid5330357">{{cite journal | vauthors = Nirenberg M, Leder P, Bernfield M, Brimacombe R, Trupin J, Rottman F, O'Neal C | title = RNA codewords and protein synthesis, VII. On the general nature of the RNA code | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 53 | issue = 5 | pages = 1161–8 | date = May 1965 | pmid = 5330357 | pmc = 301388 | doi = 10.1073/pnas.53.5.1161 | bibcode = 1965PNAS...53.1161N | doi-access = free }}</ref> Khorana, Holley and Nirenberg received the 1968 Nobel for their work.<ref name="Nobel_1968">{{cite press release |url=http://nobelprize.org/nobel_prizes/medicine/laureates/1968/index.html |title=The Nobel Prize in Physiology or Medicine 1968 |quote=The Nobel Prize in Physiology or Medicine 1968 was awarded jointly to Robert W. Holley, Har Gobind Khorana and Marshall W. Nirenberg 'for their interpretation of the genetic code and its function in protein synthesis'. |publisher=The Royal Swedish Academy of Science |date=1968 |access-date=2010-02-27}}</ref>