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James Dewey Watson

James Dewey Watson

James Dewey Watson (born April 6, 1928) is one of the discoverers of the structure of the DNA molecule. Born in Chicago, he has been fascinated by birds since he was a child due to the influence of his father. At the age of 12, he starred on the Quiz Kids, a popular radio show that challenged precocious youngsters to answer difficult questions. Thanks to the liberal policy of Robert Hutchins, he enrolled at the age of 15 at the University of Chicago. After reading Erwin Schrodinger's book What Is Life? in 1946, he changed his direction from ornithology to genetics. Watson earned a B.Sc. in Zoology in 1947. He, Francis Crick (both of the Cavendish Laboratory, Cambridge) and Maurice Wilkins (of King's College London) were awarded the 1962 Nobel Prize for Physiology or Medicine, for their determination of the structure of DNA. The contribution made by Rosalind Franklin to the discovery has been subsequently recognised in the scientific literature about the period with biographies by Anne Sayre and more recently Brenda Maddox, plus her colleague Sir Aaron Klug's Darwin Lecture in 2003, which is published by CUP in "DNA Changing Science and Society".

The Phage Group

Upon arriving at Indiana University at Bloomington to start graduate studies, Watson was attracted to the work of Salvador Luria. Luria eventually shared a Nobel prize for his work on the Luria-Delbruck experiment, which concerned the nature of genetic mutations. Luria was part of a distributed group of researchers who were making use of the viruses that infect bacteria in order to explore genetics. Luria and Max Delbrück were among the leaders of this new "Phage Group", an important movement of geneticists from experimental systems such as Drosophila towards microbial genetics. Early in 1948 Watson began his Ph.D. research in Luria's laboratory and that spring he got to meet Delbrück in Luria's apartment and again that summer during Watson's first trip to the Cold Spring Harbor Laboratory. The Phage Group was the intellectual medium within which Watson became a working scientist. Importantly, the members of the Phage Group had a sense that they were on the path to discovering the physical nature of the gene. In 1949 Watson took a course with Felix Haurowitz that included the conventional view of that time: that proteins were genes and able to replicate themselves. The other major molecular component of chromosomes, DNA, was thought by many to be a "stupid tetranucleotide", serving only a structural role to support the proteins. However, even at this early time, Watson, under the influence of the Phage Group, was aware of the work of Oswald Avery which suggested that DNA was the genetic molecule. Watson's research project involved using X-rays to inactivate bacterial viruses ("phage"). He gained his Ph.D. in Zoology at Indiana University in 1950. Watson then went to Europe for postdoctoral research, first heading to the laboratory of biochemist Herman Kalckar in Copenhagen who was interested in nucleic acids and had developed an interest in phage as an experimental system. Watson's time in Copenhagen had one favorable consequence. He was able to do some experiments with Ole Maaloe (a member of the Phage Group) that were consistent with DNA being the genetic molecule. Watson had learned about these kinds of experiments the previous summer at Cold Spring Harbor. The experiments involved radioactive phosphate as a tracer and attempted to determine what molecular components of phage particles actually infect the target bacteria during viral infection. Watson never developed a constructive interaction with Kalckar, but he did accompany Kalckar to a meeting in Italy where Watson saw Maurice Wilkins talk about his X-ray diffraction data for DNA. Watson was now certain that DNA had a definite molecular structure that could be solved. In 1951 the highly regarded Nobel Prize winning chemist Linus Pauling published his model of the protein alpha helix, a result that grew out of Pauling's relentless efforts in X-ray crystallography and molecular model building. Watson now had the desire to learn to perform X-ray diffraction experiments so that he could work to determine the structure of DNA. That summer, Luria met John Kendrew and arranged for a new postdoctoral research project for Watson in England.

The Structure of DNA

In October 1951, Watson started at the Cavendish Laboratory, the physics department of the University of Cambridge, where he met Francis Crick. Watson and Crick started an intense intellectual collaboration that in less than a year and a half resulted in their discovery of the structure of DNA. They had unique qualifications to bring to bear on the problem. Crick soon solved the mathematical equations that govern helical diffraction theory; Watson knew all of the key DNA results of the Phage Group. In April 1952, Watson's PhD research advisor, Luria, was to speak at a meeting in England. However, Luria was not allowed to travel due to cold war hysteria over his marxist leanings. Watson used Luria's speaking slot to talk about his own work with radioactive DNA and the results of others in the Phage Group that indicated the genetic material of phages was DNA. It has been recorded that during this meeting Watson was passing on to others prior discoveries by local DNA researcher Maurice Wilkins such as the calculated width of the B-form molecule as determined by X-ray diffraction studies. By 1952 estimates from X-ray data and electron microscopy agreed that the diameter of DNA was about 2 nanometers. Watson and Crick benefitted from two travel-related strokes of luck in 1952. First, Erwin Chargaff visited England in 1952 and rubbed Watson's and Crick's noses in the fact that they knew almost nothing about nucleotide biochemistry: they soon repaired their deficiency. And second, Linus Pauling did NOT visit England. His planned visit was cancelled for political reasons and he never gained access to the King's College X-ray diffraction data for DNA until it was published in 1953, along with the Watson-Crick model. With his extensive expertise, Pauling might very well have deduced the structure of DNA a year before Watson and Crick if only he had had access to this information. It was also in 1952 that the final details of the chemical structure of the DNA backbone was determined by biochemists like Alexander Todd. During 1952, Crick and Watson had been asked not to work on making molecular models of the structure of DNA. Instead, Watson's official assignment was to perform X-ray diffraction experiments on tobacco mosaic virus. Tobacco mosaic virus was the first virus to be identified (1886) and purified (1935). Since electron microscopy revealed that virus crystals form inside infected plants, it made sense to isolate this virus for study by X-ray crystallography. Early X-ray diffraction images for tobacco mosaic virus had been collected before World War II. By 1954, Watson had deduced from his X-ray diffraction images that the tobacco mosaic virus had a helical structure. But despite his official assignment, the lure of solving the puzzle of DNA structure continued to tantalize Watson; with his friend Crick, he continued to work on this topic without official sanction. Linus Pauling had made use of molecular models to solve the structure of the protein alpha helix. Could Watson and Crick similarly solve the structure of DNA? Did Watson + Crick = Pauling? Not quite. Pauling had personally attained what was possibly the world's greatest understanding of chemistry. Neither Watson nor Crick knew much chemistry. But local X-ray crystallography expert Rosalind Franklin who had already done extensive work on DNA was within easy reach in London for consultations and other key chemical knowledge they needed would drop into their laps in 1952. Building upon (some might say stealing) the unpublished X-ray diffraction research of Franklin and Wilkins, together Watson and Crick deduced the double helix structure of DNA which they published in the journal Nature on April 25, 1953. Watson's key contribution was in discovering the nucleotide base pairs that are the key to the structure and function of DNA. This key discovery was made in the Pauling "tradition", by playing with molecular models of the four nucleobases. After he realized that A:T and C:G pairs are structurally similar it was immediately clear that such structural pairing accounted for a key biochemical fact of DNA, the so-called Chargaff ratios, experimentally determined ratios of the amounts of the four nucleotide subunits of DNA: the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine. Watson's exercise in molecular modeling was facilitated by Jerry Donohue who explained to Watson and Crick the correct structures of the four bases. This allowed Watson to visually line up the complementary base pairs that could be held together by hydrogen bonds. Franklin's key contribution was when she told Watson and Crick that the phosphate backbones of DNA should be on the outside of the molecule. When Watson and Crick finally accepted this fact, the bases had to go to the inside of the DNA structure where they would have to interact chemically. Watson discovered the nature of that interaction. For their efforts, Watson, Crick, and Wilkins were awarded the Nobel Prize in Physiology or Medicine in 1962 for their discovery of DNA structure. Franklin's apparent exclusion from this Nobel Prize was due to her death in 1958 before it was awarded; unfortunately for Franklin, the Nobel Prize is not awarded posthumously. Some in the molecular biology community believe that since Franklin died early, and Wilkins was much less of a publicity-seeker, that Watson and Crick have in the popular mind overshadowed Wilkins and Franklin to an undeserved degree. In 1968 Watson wrote The Double Helix, one of the Modern Library's 100 best non-fiction books. The account is the sometimes painful story of not only the discovery of the structure of DNA, but the personalities, conflicts and controversy surrounding their work. Watson's original title was to have been "Honest Jim", in part to raise the ethical questions of sneaking around behind Franklin's back to gain access to her X-ray diffraction data before they were published. Watson seems to have never been particularly bothered by the way things turned out. If all that mattered was beating Pauling to the structure of DNA, then Franklin's cautious approach to analysis of the X-ray data was simply an obstacle that Watson needed to run around. Wilkins and others were there at the right time to help Watson and Crick do so. Also in 1968, Watson became the director of the CSHL (Cold Spring Harbor Laboratory) and made the CSHL his permanent residence in 1974. The Double Helix changed the way the public viewed scientists and the way they work. In the same way, Watson's first textbook, The Molecular Biology of the Gene set a new standard for textbooks, particularly through the use of concept heads - brief declarative subheadings. Its style has been emulated by almost all succeeding textbooks. His next great success was Molecular Biology of the Cell although here his role was more of coordinator of an outstanding group of scientist-writers. His third textbook was Recombinant DNA which used the ways in which genetic engineering has brought us so much new information about how organisms function. All the textbooks are still in print.

Genome Project

In 1988, Watson's achievement and success led to his appointment as the Head of the Human Genome Project at the National Institutes of Health, a position he held until 1992. Watson left the Genome Project after conflicts with the new NIH Director, Bernardine Healy. Watson was opposed to Healy's attempts to commercialize genes by granting patents on genes and ownership rights based on the identification of gene sequences. Watson left due to the legal technicality of it not being acceptable for the head of the Genome Project to at the same time have a job like the one Watson still held at Cold Spring Harbor Laboratory. Like his late colleague, Francis Crick, Watson is an outspoken atheist, known for his frank opinions on politics, religion, and the role of science in society. He has been considered to hold a number of controversial views. He is for instance a strong proponent of genetically modified crops, holding that the benefits far outweigh any plausible environmental dangers, and that many of the arguments against GM crops are unscientific or irrational. His views on these matters are covered in some depth in his book DNA: The Secret of Life (2003), particularly in chapter 6. He has also repeatedly said in public lectures "that if the gene (for homosexuality) were discovered and a woman decided not to give birth to a child that may have a tendency to become homosexual, she should be able to abort the fetus." [http://www.warroom.com/fadinggene.htm] In 1994, Watson gave up his position of director and became president of the CSHL for ten years. Currently, Watson gives public speeches and serves as chancellor of the Cold Spring Harbor Laboratory in Cold Spring Harbor, New York.

References

# "The properties of x-ray inactivated bacteriophage. I. Inactivation by direct effect." by J. D. Watson in Journal of Bacteriology (1950) volume 60 page 697-718. The [http://www.pubmedcentral.gov/picrender.fcgi?artid=385941&blobtype=pdf full text] of this article is available for download in PDF format. # See Chapter 2 of The Eighth Day of Creation: Makers of the Revolution in Biology by Horace Freeland Judson published by Cold Spring Harbor Laboratory Press (1996) ISBN 0879694785. # "The structure of tobacco mosaic virus. I. X-ray evidence of a helical arrangement of sub-units around the longitudinal axis" by J. D. Watson in Biochim Biophys Acta. (1954) volume 13 pages 10-19. # [http://www.nature.com/genomics/human/watson-crick/ Molecular structure of Nucleic Acids] by James D. Watson and Francis H. Crick. Nature 171, 737–738 (1953).

Further reading


- Genesis of a Discovery: DNA Structure, ed S. Chomet, King's College London 1993; published by Newman Hemisphere Press, London
- The essential reading list: [http://www.ncbe.reading.ac.uk/DNA50/reviews.html]
- [http://www.nature.com/genomics/human/watson-crick/ James D. Watson and Francis H. Crick. "Letters to Nature: Molecular structure of Nucleic Acid." Nature 171, 737–738 (1953).] Additional information about this famous journal article is at this Wikipedia page: Molecular structure of Nucleic Acids.
- James D. Watson, The Double Helix: A Personal Account of the Discovery of the Structure of DNA, Atheneum, 1980, ISBN 0689706022 (first published in 1968)
- Molecular biology of the gene (5th edition) by James D. Watson, Tania A. Baker, Stephen P. Bell, Alexander Gann, Michael Levine, Richard Losick Publisher: Benjamin Cummings (2003) ISBN: 080534635X
- James D. Watson, Genes, Girls, and Gamow: After the Double Helix, Random House, January, 2002, hardcover, 259 pages, ISBN 0375412832
- James D. Watson and Andrew Berry, DNA: The Secret of Life, Random House, April, 2003, hardcover, 464 pages, ISBN 0375415467
  -
  - [(James D. Watson/Watson, James D.)] The Double Helix: A Personal Account of the Discovery of the Structure of DNA; The Norton Critical Edition , which was published in 1980, edited by Gunther S. Stent. This book is strongly recommended for its reviews and papers for anyone interested in the history and philosophy of DNA.

External links

The British Library: "Beautiful Minds" exhibition: http://www.bl.uk/onlinegallery/features/beautifulminds/homepage.html and listen to Francis Crick on: http://www.bl.uk/onlinegallery/features/beautifulminds/sounds.html#compton
- [http://www.cshl.edu/gradschool/jdw_.html James D. Watson, Ph.D. - Cold Spring Harbor Laboratory]
- [http://www.kcl.ac.uk/depsta/ppro/dna/scientists.html The King's College London team]
- [http://www.bbc.co.uk/bbcfour/audiointerviews/profilepages/crickwatson1.shtml Audio of Francis Crick and James Watson talking on the BBC in 1962, 1972, and 1974]
- [http://nobelprize.org/medicine/laureates/1962/watson-bio.html Nobel biography]
- [http://encarta.msn.com/encyclopedia_761560789/Watson_James_Dewey.html MSN Encarta biography] for "Watson, James Dewey". Watson, James Dewey Watson Watson, James Dewey Watson, James, D. Watson, James D. Watson, James D. ko:제임스 왓슨 ja:ジェームズ・ワトソン

April 6

April 6 is the 96th day of the year in the Gregorian calendar (97th in leap years). There are 269 days remaining.

Events


- 648 BC - Earliest solar eclipse recorded by the Ancient Greeks.
- 402 - Stilicho stymies the Visigoths under Alaric in the Battle of Pollentia
- 1320 - The Scots reaffirm their independence by signing the Declaration of Arbroath.
- 1327 - The poet Petrarch first saw his idealized love Laura in the church of Saint Claire in Avignon.
- 1652 - Dutch sailor Jan van Riebeeck establishes a resupply camp at the Cape of Good Hope, which will eventually develop into Cape Town.
- 1782 - Rama I succeeds King Taksin of Thailand, who was overthrown in a coup d'état.
- 1808 - John Jacob Astor incorporates the American Fur Company.
- 1830 - The Church of Jesus Christ of Latter-day Saints is formed by Joseph Smith, Jr. at Fayette, New York.
- 1832 - Indian Wars: Black Hawk War begins - The Sauk warrior Black Hawk enters into war with the United States.
- 1841 - John Tyler is inaugurated as the 10th President of the United States.
- 1862 - American Civil War: Battle of Shiloh begins - In Tennessee, forces under Union General Ulysses S. Grant meet Confederate troops led by General Albert Sidney Johnston at Shiloh.
- 1865 - American Civil War: Battle of Sayler's Creek - Confederate General Robert E. Lee's Army of Northern Virginia fights its last major battle while in retreat from Richmond, Virginia.
- 1869 - Celluloid is patented.
- 1886 - Vancouver, British Columbia is incorporated as a city.
- 1895 - Oscar Wilde is arrested after losing a libel case against the John Sholto Douglas, 9th Marquess of Queensberry.
- 1896 - In Athens, the opening of the first modern Olympic Games after 1,500 years after being banned by Roman Emperor Theodosius I.
- 1893 - Salt Lake Temple of the Church of Jesus Christ of Latter-Day Saints dedicated by Wilford Woodruff.
- 1903 - The Kishinev pogrom in Kishinev (Bessarabia) began, forcing tens of thousands of Jews to later seek refuge in Israel and the west.
- 1909 - Robert Peary allegedly reaches the North Pole.
- 1911 - Dedë Gjon Luli Dedvukaj, Leader of the Malësori Albanians raises the Albanian flag in the town of Tuzi, Montenegro for the first time after Gjergj Kastrioti (Skenderbeg).
- 1917 - World War I: United States declares war on Germany (see [http://en.wikisource.org/wiki/Woodrow_Wilson_declares_war_on_Germany Wilson's address to Congress]).
- 1926 - Walter Varney Airlines makes first commercial flight from Pasco, Washington, to Elko, Nevada. Varney is the root company of United Airlines.
- 1930 - Gandhi raised a lump of mud and salt (some say just a pinch, some say just a grain) and declared, "With this, I am shaking the foundations of the British Empire." Thus he started Salt Satyagraha.
- 1930 - Hostess Twinkies are invented.
- 1930 - Will Rogers starts broadcasting The Will Rogers Program on radio.
- 1931 - Little Orphan Annie debuts on the Blue Network of NBC.
- 1936 - Tupelo-Gainesville Outbreak: Another tornado from the same storm system as the Tupelo tornado hits Gainesville, Georgia, killing 203.
- 1941 - World War II: Operation Castigo begins - Germany invades Kingdom of Yugoslavia and Greece.
- 1965 - Early Bird, the first communications satellite to be placed in synchronous orbit, is launched.
- 1968 - In London, United Kingdom, Massiel wins the thirteenth Eurovision Song Contest for Spain singing "La, la, la."
- 1970 - Four California Highway Patrol officers die in one of the worst cop killings in the CHP's history; this is known as the Newhall Incident.
- 1972 - Vietnam War: Easter Offensive - The first day of clear weather in three days allows American forces to start sustained air strikes and naval bombardments.
- 1973 - Launch of Pioneer 11 spacecraft.
- 1974 - The California Jam Rock concert begins.
- 1974 - In Brighton, United Kingdom, ABBA wins the nineteenth Eurovision Song Contest for Sweden singing "Waterloo."
- 1984 - Members of Cameroon's Republican Guard from country's northern region attack various government buildings in an unsuccessful attempt to overthrow the government headed by Paul Biya.
- 1987 - Sugar Ray Leonard takes the middleweight boxing title from Marvin Hagler.
- 1993 - Russian nuclear accident at Tomsk 7.
- 1994 - The Rwandan Genocide begins when the aircraft carrying Rwandan president Juvénal Habyarimana and Burundian president Cyprien Ntaryamira is shot down by extremists.
- 1998 - Pakistan tests medium-range missiles capable of hitting India.
- 1998 - The Dow Jones Industrial Average gains 49.82 to close at 9,033.23 -- its first-ever close above 9,000.
- 2001 - Miller Park opens in Milwaukee, Wisconsin.
- 2004 - Rolandas Paksas becomes the first president to be peacefully removed from the post by impeachment.

Births


- 1483 - Raphael, Italian painter and architect (d. 1520)
- 1651 - André Dacier, French classical scholar (d. 1722)
- 1664 - Arvid Horn, Swedish statesman (d. 1742)
- 1671 - Jean-Baptiste Rousseau, French poet (d. 1741)
- 1725 - Pasquale Paoli, Corsican patriot and military leader (d. 1807)
- 1812 - Alexander Herzen, Russian writer (d. 1870)
- 1815 - Robert Volkmann, German composer (d. 1883)
- 1818 - Aasmund Olavsson Vinje, Norwegian poet (d. 1870)
- 1820 - Nadar, French photographer (d. 1910)
- 1823 - Joseph Medill, Mayor of Chicago (d. 1899)
- 1826 - Gustave Moreau, French painter (d. 1898)
- 1866 - Butch Cassidy, American outlaw (d. 1909)
- 1878 - Erich Mühsam, German author (d. 1934)
- 1884 - Walter Huston, Canadian-born actor (d. 1950)
- 1890 - Anthony Fokker, Dutch designer of aircraft (d. 1939)
- 1892 - Donald Wills Douglas, Sr., American industrialist (d. 1981)
- 1892 - Lowell Thomas, American travel writer (d. 1981)
- 1902 - Veniamin Kaverin, Russian writer (d. 1989)
- 1903 - Mickey Cochrane, baseball player (d. 1962)
- 1903 - Doc Edgerton, American electrical engineer (d. 1990)
- 1911 - Feodor Felix Konrad Lynen, German biochemist, recipient of the Nobel Prize in Physiology or Medicine (d. 1979)
- 1920 - Edmond H. Fischer, Swiss-American biochemist, recipient of the Nobel Prize in Physiology or Medicine
- 1926 - Sergio Franchi, Italian-born singer and actor (d. 1990)
- 1926 - Gil Kane, Latvian-born cartoonist (d. 2000)
- 1926 - Ian Paisley, British politician
- 1927 - Gerry Mulligan, American musician (d. 1996)
- 1928 - James D. Watson, American geneticist, recipient of the Nobel Prize in Physiology or Medicine
- 1929 - André Previn, German-born composer and conductor
- 1931 - Ivan Dixon, American actor and director
- 1933 - Roy Goode, British lawyer
- 1934 - Anton Geesink, Dutch judoka
- 1937 - Merle Haggard, American musician
- 1937 - Billy Dee Williams, American actor
- 1938 - Paul Daniels, English magician
- 1938 - Roy Thinnes, American actor
- 1941 - Phil Austin, American comedian
- 1941 - Zamfir, Romanian musician
- 1942 - Barry Levinson, American film producer and director
- 1944 - Felicity Palmer, English soprano
- 1947 - John Ratzenberger, American actor
- 1949 - Horst Ludwig Störmer, German-born physicist, Nobel Prize laureate
- 1951 - Bert Blyleven, Dutch Major League Baseball player
- 1952 - Udo Dirkschneider, German singer (Accept and U.D.O.)
- 1952 - Marilu Henner, American actress
- 1954 - Thom Bray, American actor
- 1955 - Michael Rooker, American actor
- 1965 - Frank Black, American singer and songwriter (Pixies)
- 1969 - Bison Dele, American basketball player (disappeared 2002)
- 1969 - Ari Meyers, Puerto Rican actress
- 1970 - Olaf Kölzig, South African hockey player
- 1973 - Rie Miyazawa, Japanese actress and singer
- 1975 - Zach Braff, American actor
- 1976 - Candace Cameron, American actress

Deaths


- 1199 - King Richard I of England (killed in battle) (b. 1157)
- 1362 - James I, Count of La Marche, French soldier (b. 1319)
- 1490 - King Matthias Corvinus of Hungary
- 1520 - Raphael, Italian painter and architect (b. 1483)
- 1528 - Albrecht Dürer, German artist (b. 1471)
- 1551 - Joachim Vadian, Swiss humanist (b. 1484)
- 1571 - John Hamilton, Scottish prelate and politician
- 1590 - Francis Walsingham, English spymaster
- 1605 - John Stow, English historian
- 1655 - David Blondel, French protestant clergyman (b. 1591)
- 1686 - Arthur Annesley, 1st Earl of Anglesey, English royalist statesman (b. 1614)
- 1707 - Willem van de Velde, the younger, Dutch painter (b. 1633)
- 1755 - Richard Rawlinson, English minister and antiquarian (b. 1690)
- 1829 - Niels Henrik Abel, Norwegian mathematician (b. 1802)
- 1862 - Albert Sidney Johnston, American Confederate general (b. 1803)
- 1883 - Benjamin Raymond, Mayor of Chicago (b. 1801)
- 1906 - Alexander Kielland, Norwegian author (b. 1849)
- 1935 - Edwin Arlington Robinson, American poet (b. 1869)
- 1961 - Jules Bordet, Belgian immunologist and microbiologist, recipient of the Nobel Prize in Physiology or Medicine (b. 1870)
- 1963 - Otto Struve, Russian-born astronomer (b. 1897)
- 1970 - Sam Sheppard, American accused murderer (b. 1923)
- 1971 - Igor Stravinsky, Russian composer (b. 1882)
- 1974 - Willem Marinus Dudok, Dutch architect (b. 1884)
- 1986 - Raimundo Orsi, Argentine-Italian footballer
- 1992 - Isaac Asimov, Russian-born author (b. 1920)
- 1994 - Juvénal Habyarimana, President of Rwanda (b. 1937)
- 1994 - Cyprien Ntaryamira, President of Burundi (b. 1956)
- 1996 - Greer Garson, Irish actress (b. 1904)
- 1998 - Wendy O. Williams, American musician (Plasmatics) (b. 1949)
- 1998 - Tammy Wynette, American musician (b. 1942)
- 2000 - Habib Bourguiba, President of Tunisia (b. 1903)
- 2003 - David Bloom, American reporter (pulmonary embolism) (b. 1963)
- 2003 - Babatunde Olatunji, Nigerian drummer (b. 1927)
- 2004 - Larisa Bogoraz, Soviet dissident (b. 1929)
- 2005 - Rainier III, Prince of Monaco (b. 1923)

Holidays and observances


- Feast day of St. Sixtus and Marcellinus of Carthage in the Roman Catholic Church.
- The start of the tax year in the United Kingdom (arising from the 11 day correction to March 25 at the adoption of the Gregorian calendar in 1752).
- Tartan Day, a day set aside for the celebration of the Scottish influence on America.
- Community of Christ Birthday, a day of importance to some members of Community of Christ as it is the anniversary of when it was officially organized on April 6 1830CE.

External links


- [http://news.bbc.co.uk/onthisday/hi/dates/stories/april/6 BBC: On This Day]
- [http://www.tnl.net/when/4/6 Today in History: April 6] ----- April 5 - April 7 - March 6 - May 6 -- listing of all days ko:4월 6일 ja:4月6日 simple:April 6 th:6 เมษายน

DNA

:For other uses, see DNA (disambiguation). DNA (disambiguation) Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and most viruses). DNA is a long polymer of nucleotides and encodes the sequence of the amino acid residues in proteins using the genetic code, a triplet code of nucleotides. In complex cells (eukaryotes), such as those from plants, animals, fungi and protists, most of the DNA is located in the cell nucleus. By contrast, in simpler cells called prokaryotes (the eubacteria and archaea), DNA is not separated from the cytoplasm by a nuclear envelope. The cellular organelles known as chloroplasts and mitochondria also carry DNA. DNA is often referred to as the molecule of heredity as it is responsible for the genetic propagation of most inherited traits. These traits can range from hair colour to disease susceptibility. During cell division, DNA is replicated and can be transmitted to offspring during reproduction. Lineage studies can be done based on the facts that the DNA in mitochondria (mitochondrial DNA) only comes from the mother, and the male "Y" chromosome only comes from the father. Every person's DNA, their genome, is inherited from both parents. The mother's mitochondrial DNA together with twenty-three chromosomes from each parent combine to form the genome of a fertilized egg. As a result, with certain exceptions such as red blood cells, most human cells contain 23 pairs of chromosomes, together with mitochondrial DNA inherited from the mother.

DNA Overview

red blood cell This section presents an introductory and therefore incomplete overview of DNA.
- Genes can be loosely viewed as the organism's "cookbook" or "blueprint";
- A strand of DNA contains genes, areas that regulate genes, and areas that either have no function, or a function we do not (yet) know (also see last bullet point in this section for the difference between DNA and RNA);
- DNA is organized as two complementary strands, head-to-toe, with bonds between them that can be "unzipped" like a zipper, separating the strands;
- DNA is a chain of chemical "building blocks", called "bases", of which there are four types: these can be abbreviated A, T, C, and G. Each base can only "pair up" with one single predetermined other base: A+T, T+A, C+G and G+C are the only possible combinations; that is, an "A" on one strand of double-stranded DNA will "mate" properly only with a "T" on the other, complementary strand;
  - N.B.: U occasionally replaces T, notably in PBS1 phage DNA; you can thus substitute "U" for "T" throughout this section.
- Because each strand of DNA has a directionality, the sequence order does matter: A+T is not the same as T+A, just as C+G is not the same as G+C;
- For each given base, there is just one possible complementary base, so naming the bases on the conventionally chosen side of the strand is enough to describe the entire double-strand sequence;
- The genetic information contained in a strand of DNA is determined by the sequence of bases along its length;
- The cell begins DNA replication by forcibly unzipping the DNA double strand down the middle, and then recreates the "other half" of each new single strand by drowning each half in a "soup" made of the four bases. An enzyme makes a new strand by finding the correct "base" in the soup and pairing it with the original strand. In this way, the base on the old strand dictates which base will be on the new strand, and the cell ends up with an extra copy of its DNA.
- Mutations are simply chemical imperfections in this process: a base is accidentally skipped, inserted, or incorrectly copied, or the chain is trimmed, or added to; many basic mutations can be described as combinations of these accidental "operations". Mutations can also occur through chemical damage (through mutagens), light (UV damage), or through other more complicated gene swapping events.
- DNA (for DeoxyriboNucleic Acid) differs from RNA (for RiboNucleic Acid) by having the sugar 2-deoxyribose instead of ribose in its backbone (ribose contains one extra oxygen atom compared to deoxyribose -- in other words, DNA contains deoxygenated ribose, whereas RNA contains "plain" ribose.) This is the basic chemical distinction between RNA and DNA.

DNA in practice

DNA in crime

Forensic scientists can use DNA located in blood, semen, skin, saliva, or hair left at the scene of a crime to identify a possible suspect, a process called genetic fingerprinting or DNA profiling. In DNA profiling the relative lengths of sections of repetitive DNA, such as short tandem repeats and minisatellites, are compared. DNA profiling was developed in 1984 by English geneticist Alec Jeffreys, and was first used in 1986 in the Enderby murders case in Leicestershire, England. Many jurisdictions require convicts of certain types of crimes to provide a sample of DNA for inclusion in a computerized database. This has helped investigators solve old cases where the perpetrator was unknown and only a DNA sample was obtained from the scene (particularly in rape cases between strangers). This method is one of the most reliable techniques for identifying a criminal, but is not always perfect, for example if no DNA can be retrieved, or if the scene is contaminated with the DNA of several possible suspects.

DNA in computation

Despite its biological origins, DNA plays an important role in computer science, both as a motivating research problem and as a method of computation in itself, called DNA computing. As a simple example, research on string searching algorithms, which find an occurrence of a sequence of letters inside a larger sequence of letters, was motivated by DNA research, where it is used to find specific sequences of nucleotides in a large sequence. In other applications like text editors, even simple algorithms for this problem usually suffice, but DNA sequences cause these algorithms to exhibit near-worst-case behavior due to their small number of distinct characters. Databases have also been strongly motivated by DNA research, which requires special tools for storing and manipulating DNA sequences. Databases specialized for this purpose are called genomic databases, and have a number of unique technical challenges associated with the operations of approximate matching, sequence comparison, finding repeating patterns, and homology searching. In 1994, Leonard Adleman of the University of Southern California made headlines when he discovered a way of solving the directed Hamiltonian path problem, an NP-complete problem, using tools from molecular biology, in particular DNA. The new approach, dubbed DNA computing, has practical advantages over traditional computers in power use, space use, and efficiency, due to its ability to highly parallelize the computation (see parallel computing)(there is labor worth mention involved in retrieving answers computed these computational DNA techniques.). A number of other problems, including simulation of various abstract machines, the boolean satisfiability problem, and the bounded version of the Post correspondence problem, have since been analyzed using DNA computing. Due to its compactness, DNA also has an important role in cryptography, where in particular it allows unbreakable one-time pads to be efficiently constructed and used.[http://citeseer.ist.psu.edu/gehani99dnabased.html]

Overview of molecular structure

one-time pad Although sometimes called "the molecule of heredity", pieces of DNA as people typically think of them are not single molecules. Rather, they are pairs of molecules, which entwine like vines to form a double helix (see the illustration at the right). Each vine-like molecule is a strand of DNA: a chemically linked chain of nucleotides, each of which consists of a sugar, a phosphate and one of five kinds of nucleobases ("bases"). Because DNA strands are composed of these nucleotide subunits, they are polymers. The diversity of the bases means that there are five kinds of nucleotides, which are commonly referred to by the identity of their bases. These are adenine (A), thymine (T), uracil (U), cytosine (C), and guanine (G). U is rarely found in DNA except as a result of chemical degradation of C, but in some viruses, notably PBS1 phage DNA, U completely replaces the usual T in its DNA. Similarly, RNA usually contains U in place of T, but in certain RNAs such as transfer RNA, T is always found in some positions. Thus, the only true difference between DNA and RNA is the sugar, 2-deoxyribose in DNA and ribose in RNA. In a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect and pi stacking. Specificity of which strands stay associated is determined by complementary pairing. Each base forms hydrogen bonds readily to only one other -- A to T and C to G -- so that the identity of the base on one strand dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association. The cell's machinery is capable of melting or disassociating a DNA double helix, and using each DNA strand as a template for synthesizing a new strand which is nearly identical to the previous strand. Errors that occur in the synthesis are known as mutations. The process known as PCR (polymerase chain reaction) mimics this process in vitro in a nonliving system. Because pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside; the two chains they form are sometimes called the "backbones" of the helix. In fact, it is chemical bonds between the phosphates and the sugars that link one nucleotide to the next in the DNA strand.

The role of the sequence

Within a gene, the sequence of nucleotides along a DNA strand defines a messenger RNA sequence which then defines a protein, that an organism is liable to manufacture or "express" at one or several points in its life using the information of the sequence. The relationship between the nucleotide sequence and the amino-acid sequence of the protein is determined by simple cellular rules of translation, known collectively as the genetic code. The genetic code is made up of three-letter 'words' (termed a codon) formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). These codons can then be translated with messenger RNA and then transfer RNA, with a codon corresponding to a particular amino acid. There are 64 possible codons (4 bases in 3 places 4^3) that encode 20 amino acids. Most amino acids, therefore, have more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region, namely the UAA, UGA and UAG codons. In many species, only a small fraction of the total sequence of the genome appears to encode protein. For example, only about 1.5% of the human genome consists of protein-coding exons. The function of the rest is a matter of speculation. It is known that certain nucleotide sequences specify affinity for DNA binding proteins, which play a wide variety of vital roles, in particular through control of replication and transcription. These sequences are frequently called regulatory sequences, and researchers assume that so far they have identified only a tiny fraction of the total that exist. "Junk DNA" represents sequences that do not yet appear to contain genes or to have a function. The reasons for the presence of so much non-coding DNA in eukaryotic genomes and the extraordinary differences in genome size ("C-value") among species represent a long-standing puzzle in DNA research known as the "C-value enigma". Some DNA sequences play structural roles in chromosomes. Telomers and centromeres typically contain few (if any) protein-coding genes, but are important for the function and stability of chromosomes. Some genes code for "RNA genes" (see tRNA and rRNA). Some RNA genes code for transcripts that function as regulatory RNAs (see siRNA) that influence the function of other RNA molecules. The intron-exon structure of some genes (such as immunoglobin and protocadeherin genes) is important for allowing alternative splicing of pre-mRNA which allows several different proteins to be made from the same gene. Some non-coding DNA represents pseudogenes that can be used as raw material for the creation of new genes with new functions. Some non-coding DNA provided hot-spots for duplication of short DNA regions; such sequence duplication has been the major form of genetic change in the human lineage (see evidence from the Chimpanzee Genome Project). Exons interspersed with introns allows for "exon shuffling" and the creation of modified genes that might have new adaptive functions. Large amounts of non-coding DNA is probably adaptive in that it provides chromosomal regions where recombination between homologous portions of chromosomes can take place without disrupting the function of genes. Some biologists such as Stuart Kauffman have speculated that there must be mechanisms by which the rate of evolution of a species can be increased or decreased. Non-coding DNA provides mechanisms for gene creation, modification and recombination it is probably important for control of the rate of human evolution. Sequence also determines a DNA segment's susceptibility to cleavage by restriction enzymes, the quintessential tools of genetic engineering. The position of cleavage sites throughout an individual's genome determines one kind of an individual's "DNA fingerprint".

DNA replication

Main article: DNA replication DNA replication DNA replication or DNA synthesis is the process of copying the double-stranded DNA prior to cell division. The two resulting double strands are generally almost perfectly identical, but occasionally errors in replication can result in a less than perfect copy (see mutation), and each of them consists of one original and one newly synthesized strand. This is called semiconservative replication. The process of replication consists of three steps: initiation, replication and termination.

Mechanical properties relevant to biology

Main article: Mechanical properties of DNA.

Strands association and dissociation

The hydrogen bonds between the strands of the double helix are weak enough that they can be easily separated by enzymes. Enzymes known as helicases unwind the strands to facilitate the advance of sequence-reading enzymes such as DNA polymerase. The unwinding requires that helicases chemically cleave the phosphate backbone of one of the strands so that it can swivel around the other. The strands can also be separated by gentle heating, as used in PCR, provided they have fewer than about 10,000 base pairs (10 kilobase pairs, or 10 kbp). The intertwining of the DNA strands makes long segments difficult to separate.

Circular DNA

When the ends of a piece of double-helical DNA are joined so that it forms a circle, as in plasmid DNA, the strands are topologically knotted. This means they cannot be separated by gentle heating or by any process that does not involve breaking a strand. The task of unknotting topologically linked strands of DNA falls to enzymes known as topoisomerases. Some of these enzymes unknot circular DNA by cleaving two strands so that another double:stranded segment can pass through. Unknotting is required for the replication of circular DNA as well as for various types of recombination in linear DNA.

Great length versus tiny breadth

The narrow breadth of the double helix makes it impossible to detect by conventional electron microscopy, except by heavy staining. At the same time, the DNA found in many cells can be macroscopic in length -- approximately 5 centimetres long for strands in a human chromosome. Consequently, cells must compact or "package" DNA to carry it within them. This is one of the functions of the chromosomes, which contain spool-like proteins known as histones, around which DNA winds.

Entropic stretching behavior

When DNA is in solution, it undergoes conformational fluctuations due to the energy available in the thermal bath. For entropic reasons, more floppy states are thermally accessible than stretched out states; for this reason, a single molecule of DNA stretches similarly to a rubber band. Using optical tweezers, the entropic stretching behavior of DNA has been studied and analyzed from a polymer physics perspective, and it has been found that DNA behaves like the Kratky-Porod worm-like chain model with a persistence length of about 53 nm. Furthermore, DNA undergoes a stretching phase transition at a force of 65 pN; above this force, DNA is thought to take the form that Linus Pauling originally hypothesized, with the phosphates in the middle and bases splayed outward. This proposed structure for overstretched DNA has been called "P-form DNA," in honor of Pauling.

Different helix geometries

The DNA helix can assume one of three slightly different geometries, of which the "B" form described by James D. Watson and Francis Crick is believed to predominate in cells. It is 2 nanometres wide and extends 3.4 nanometres per 10 bp of sequence. This is also the approximate length of sequence in which the double helix makes one complete turn about its axis. This frequency of twist (known as the helical pitch) depends largely on stacking forces that each base exerts on its neighbors in the chain.

Supercoiled DNA

The B form of the DNA helix twists 360° per 10.6 bp in the absence of strain. But many molecular biological processes can induce strain. A DNA segment with excess or insufficient helical twisting is referred to, respectively, as positively or negatively "supercoiled". DNA in vivo is typically negatively supercoiled, which facilitates the unwinding of the double-helix required for RNA transcription.

Sugar pucker

There are four conformations that the ribofuranose rings in nucleotides can acquire: # C-2' endo # C-2' exo # C-3' endo # C-3' exo Ribose is usually in C-3'endo, while deoxyribose is usually in the C-2' endo sugar pucker conformation. The A and B forms differ mainly in their sugar pucker. In the A form, the C3' configuration is above the sugar ring, whilst the C2' configuration is below it. Thus, the A form is described as "C3'-endo." Likewise, in the B form, the C2' configuration is above the sugar ring, whilst C3' is below; this is called "C2'-endo." Altered sugar puckering in A-DNA results in shortening the distance between adjacent phosphates by around one angstrom. This gives 11 to 12 base pairs to each helix in the DNA strand, instead of 10.5 in B-DNA. Sugar pucker gives uniform ribbon shape to DNA, a cylindrical open core, and also a deep major groove more narrow and pronounced that grooves found in B-DNA.

Conditions for formation of A and Z helices

The two other known double-helical forms of DNA, called A and Z, differ modestly in their geometry and dimensions. The A form appears likely to occur only in dehydrated samples of DNA, such as those used in crystallographic experiments, and possibly in hybrid pairings of DNA and RNA strands. Segments of DNA that cells have methylated for regulatory purposes may adopt the Z geometry, in which the strands turn about the helical axis like a mirror image of the B form.

Table of comparison of the properties of different helical forms

Non-helical forms

Other, including non-helical, forms of DNA have been described, for example a side-by-side (SBS) configuration. Indeed, it is far from certain that the B-form double helix is the dominant form in living cells.

Direction of DNA strands

The asymmetric shape and linkage of nucleotides means that a DNA strand always has a discernible orientation or directionality. Because of this directionality, close inspection of a double helix reveals that nucleotides are heading one way along one strand (the "ascending strand"), and the other way along the other strand (the "descending strand"). This arrangement of the strands is called antiparallel.

Chemical nomenclature (5' and 3')

For reasons of chemical nomenclature, people who work with DNA refer to the asymmetric ends of ("five prime" and "three prime"). Biologists and the DNA enzymes they use, predominantly read nucleotide sequences in the "5' to 3' direction". However, because chemically produced DNA is synthesized and manipulated in the opposite or in non-directional manners, the orientation should not be assumed. In a vertically oriented double helix, the 3' strand is said to be ascending while the 5' strand is said to be descending.

Sense and antisense

As a result of their antiparallel arrangement and the sequence-reading preferences of enzymes, even if both strands carried identical instead of complementary sequences, cells could properly translate only one of them. The other strand a cell can only read backwards. Molecular biologists call a sequence "sense" if it is translated or translatable, and they call its complement "antisense". It follows then, somewhat paradoxically, that the template for transcription is the antisense strand. The resulting transcript is an RNA replica of the sense strand and is itself sense.

Distinction between sense and antisense strands

A small proportion of genes in prokaryotes, and more in plasmids and viruses, blur the distinction made above between sense and antisense strands. Certain sequences of their genomes do double duty, encoding one protein when read 5' to 3' along one strand, and a second protein when read in the opposite direction (still 5' to 3') along the other strand. As a result, the genomes of these viruses are unusually compact for the number of genes they contain, which biologists view as an adaptation. This merely confirms that there is no biological distinction between the two strands of the double helix. Indeed, typically each strand of a DNA double helix will act as sense and antisense in different regions.

As viewed by topologists

Topologists like to note that the juxtaposition of the 3′ end of one DNA strand beside the 5′ end of the other at both ends of a double-helical segment makes the arrangement a "crab canon".

Single-stranded DNA (ssDNA) and repair of mutations

In some viruses DNA appears in a non-helical, single-stranded form. Because many of the DNA repair mechanisms of cells work only on paired bases, viruses that carry single-stranded DNA genomes mutate more frequently than they would otherwise. As a result, such species may adapt more rapidly to avoid extinction. The result would not be so favorable in more complicated and more slowly replicating organisms, however, which may explain why only viruses carry single-stranded DNA. These viruses presumably also benefit from the lower cost of replicating one strand versus two.

The history of DNA research

mutate at the University of Cambridge]] The discovery that DNA was the carrier of genetic information was a process that required many earlier discoveries. The existence of DNA was discovered in the mid 19th century. However, it was only in the early 20th century that researchers began suggesting that it might store genetic information. This was only accepted after the structure of DNA was elucidated by Watson and Crick in their 1953 Nature publication. Watson and Crick proposed the central dogma of molecular biology in 1957, describing the process whereby proteins are produced from nucleic DNA.

First isolation of DNA

Working in the 19th century, biochemists initially isolated DNA and RNA (mixed together) from cell nuclei. They were relatively quick to appreciate the polymeric nature of their "nucleic acid" isolates, but realized only later that nucleotides were of two types--one containing ribose and the other deoxyribose. It was this subsequent discovery that led to the identification and naming of DNA as a substance distinct from RNA. Friedrich Miescher (1844-1895) discovered a substance he called "nuclein" in 1869. Somewhat later, he isolated a pure sample of the material now known as DNA from the sperm of salmon, and in 1889 his pupil, Richard Altmann, named it "nucleic acid". This substance was found to exist only in the chromosomes. In 1929 Phoebus Levene at the Rockefeller Institute identified the components (the four bases, the sugar and the phosphate chain) and he showed that the components of DNA were linked in the order phosphate-sugar-base. He called each of these units a nucleotide and suggested the DNA molecule consisted of a string of nucleotide units linked together through the phosphate groups, which are the 'backbone' of the molecule. However Levene thought the chain was short and that the bases repeated in the same fixed order. Torbjorn Caspersson and Einar Hammersten showed that DNA was a polymer.

Establishing a link between heritable traits and chromosomes

Max Delbrück, Nikolai V. Timofeeff-Ressovsky, and Karl G. Zimmer published results in 1935 suggesting that chromosomes are very large molecules the structure of which can be changed by treatment with X-rays, and that by so changing their structure it was possible to change the heritable characteristics governed by those chromosomes. In 1937 William Astbury produced the first X-ray diffraction patterns from DNA. He was not able to propose the correct structure but the patterns showed that DNA had a regular structure and therefore it might be possible to deduce what this structure was. In 1943, Oswald Theodore Avery discovered that traits proper to the "smooth" form of the Pneumococcus could be transferred to the "rough" form of the same bacteria merely by making the killed "smooth" (S) form available to the live "rough" (R) form. Quite unexpectedly, the living R Pneumococcus bacteria were transformed into a new strain of the S form, and the transferred S characteristics turned out to be heritable. Avery called the medium of transfer of traits the transforming principle; he identified DNA as the transforming principle, and not protein as previously thought. In 1953, Alfred Hershey and Martha Chase did an experiment (Hershey-Chase experiment) that showed, in T2 phage, that DNA is the genetic material (Hershey shared the Nobel prize with Luria). genetic material double-helix pattern]] In 1944, the renowned physicist, Erwin Schrödinger, published a brief book entitled What is Life?, where he maintained that chromosomes contained what he called the "hereditary code-script" of life. He added: "But the term code-script is, of course, too narrow. The chromosome structures are at the same time instrumental in bringing about the development they foreshadow. They are law-code and executive power -- or, to use another simile, they are architect's plan and builder's craft -- in one." He conceived of these dual functional elements as being woven into the molecular structure of chromosomes. By understanding the exact molecular structure of the chromosomes one could hope to understand both the "architect's plan" and also how that plan was carried out through the "builder's craft." Three groups took up Schrödinger's challenge to work out the structure of the chromosomes and the question of how the segments of the chromosomes that were conceived to relate to specific traits could possibly do their jobs. Just how the presence of specific features in the molecular structure of chromosomes could produce traits and behaviors in living organisms was unimaginable at the time. Because chemical dissection of DNA samples always yielded the same four nucleotides, the chemical composition of DNA appeared simple, perhaps even uniform. Organisms, on the other hand, are fantastically complex individually and widely diverse collectively. Geneticists did not speak of genes as conveyors of "information" in such words, but if they had, they would not have hesitated to quantify the amount of information that genes need to convey as vast. The idea that information might reside in a chemical in the same way that it exists in text--as a finite alphabet of letters arranged in a sequence of unlimited length--had not yet been conceived. It would emerge upon the discovery of DNA's structure, but few researchers imagined that DNA's structure had much to say about genetics.

Discovery of the structure of DNA

In the 1950s, three groups made it their goal to determine the structure of DNA. The first group to start was at King's College London and was led Maurice Wilkins and was later joined by Rosalind Franklin. Another group consisting of Francis Crick and James D. Watson was at Cambridge. A third group was at CalTech and was led by Linus Pauling. Crick and Watson built physical models using metal rods and balls, in which they incorporated the known chemical structures of the nucleotides, as well as the known position of the linkages joining one nucleotide to the next along the polymer. At King's College Maurice Wilkins and Rosalind Franklin examined X-ray diffraction patterns of DNA fibers. Of the three groups, only the London group was able to produce good quality diffraction patterns and thus produce sufficient quantitative data about the structure X-ray diffraction

Discovery that DNA is helical

In 1948 Pauling discovered that many proteins included helical (see alpha helix) shapes. Pauling had deduced this structure from X-ray patterns. (Pauling was also later to suggest an incorrect three chain helical structure based on Astbury's data.) Even in the initial diffraction data from DNA by Maurice Wilkins, it was evident that the structure involved helices. But this insight was only a beginning. There remained the questions of how many strands came together, whether this number was the same for every helix, whether the bases pointed toward the helical axis or away, and ultimately what were the explicit angles and coordinates of all the bonds and atoms. Such questions motivated the modeling efforts of Watson and Crick.

Discovery that complementary nucleotides occur in equal proportions

In their modeling, Watson and Crick restricted themselves to what they saw as chemically and biologically reasonable. Still, the breadth of possibilities was very wide. A breakthrough occurred in 1952, when Erwin Chargaff visited Cambridge and inspired Crick with a description of experiments Chargaff had published in 1947. Chargaff had observed that the proportions of the four nucleotides vary between one DNA sample and the next, but that for particular pairs of nucleotides -- adenine and thymine, guanine and cytosine -- the two nucleotides are always present in equal proportions.

Watson and Crick's model

1947 Watson and Crick had begun to contemplate double helical arrangements, but they lacked information about the amount of twist (pitch) and the distance between the two strands. Rosalind Franklin had to disclose some of her findings for the Medical Research Council and Crick saw this material through Max Perutz's links to the MRC. Franklin's work confirmed a double helix that was on the outside of the molecule and also gave an insight into its symmetry, in particular that the two helical strands ran in opposite directions. Watson and Crick were again greatly assisted by more of Franklin's data. This is controversial because Franklin's critical X-ray pattern was shown to Watson and Crick without Franklin's knowledge or permission. Wilkins showed the famous Photo 51 to Watson at his lab immediately after Watson had been unsuccessful in asking Franklin to collaborate to beat Pauling in finding the structure. From the data in photograph 51 Watson and Crick were able to discern that not only was the distance between the two strands was constant, but also to measure its exact value of 2 nanometres. The same photograph also gave them the 3.4 nanometre-per-10 bp "pitch" of the helix. The final insight came when Crick and Watson saw that a complementary pairing of the bases could provide an explanation for Chargaff's puzzling finding. However the structure of the bases had been incorrectly guessed in the textbooks as the enol tautomer when they were more likely to be in the keto form. When Jerry Donohue pointed this fallacy out to Watson, Watson quickly realised that the pairs of adenine and thymine, and guanine and cytosine were almost identical in shape and so would provide equally sized 'rungs' between the two strands. With the base-pairing, the Watson and Crick quickly converged upon a model, which they announced before Franklin herself had published any of her work. Franklin was two steps away from the solution. She had not guessed the base-pairing and had not appreciated the implications of the symmetry that she had described. However she had been working almost alone and did not have regular contact with a partner like Crick and Watson, and with other experts such as Jerry Donohoe. Her notebooks show that she was aware both of Jerry Donohue's work concerning tautomeric forms of bases (she used the keto forms for three of the bases) and of Chargaff's work. The disclosure of Franklin's data to Watson has angered some people who believe Franklin did not receive due credit at the time and that she might have discovered the structure on her own before Crick and Watson. In Crick and Watson's famous paper in Nature in 1953, they said that their work had been stimulated by the work of Wilkins and Franklin, whereas it had been the basis of their work. However they had agreed with Wilkins and Franklin that they all should publish papers in the same issue of Nature in support of the proposed structure.

Publishing of the "Central Dogma"

Watson and Crick's model attracted great interest immediately upon its presentation. Arriving at their conclusion on February 21 1953, Watson and Crick made their first announcement on February 28. Their paper [http://www.nature.com/genomics/human/watson-crick/ 'A Structure for Deoxyribose Nucleic Acid'] was published on April 25. In an influential presentation in 1957, Crick laid out the "Central Dogma", which foretold the relationship between DNA, RNA, and proteins, and articulated the "sequence hypothesis." A critical confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 in the form of the Meselson-Stahl experiment. Work by Crick and coworkers showed that the genetic code was based on non-overlapping triplets of codons, and Har Gobind Khorana and others deciphered the genetic code not long afterward. These findings represent the birth of molecular biology. Watson, Crick, and Wilkins were awarded the 1962 Nobel Prize for Physiology or Medicine for discovering the molecular structure of DNA, by which time Franklin had died. Nobel prizes are not awarded posthumously; had she lived, the difficult decision over whom to jointly award the prize would have been complicated as the prize can only be shared between two or three. The process of the actual nomination is covered in Graeme Hunter's biography of Sir Lawrence Bragg, "Light is a Messenger" (pub. 2004)

Bibliography


- DNA: The Secret of Life, by James D. Watson. ISBN 0-375-41546-7
- The Double Helix: A Personal Account of the Discovery of the Structure of DNA (Norton Critical Editions), by James D. Watson. ISBN 0393950751

External links


- Extensive online guide to the life and work of Francis Crick, O.M. compiled by Martin Packer, Birmingham (England): http://www.packer34.freeserve.co.uk/rememberingfranciscrickacelebration.htm martin@packer34.freeserve.co.uk; recollections of Francis Crick (for publication) for the forthcoming biography would be very much appreciated as soon as possible.
- Listen to Francis Crick and James Watson talking on the BBC in 1962, 1972, and 1974: http://www.bbc.co.uk/bbcfour/audiointerviews/profilepages/crickwatson1.shtml
- [http://news.bbc.co.uk/1/hi/sci/tech/2949629.stm 17 April, 2003, BBC News: Most ancient DNA ever?]
- [http://www.whatsnextnetwork.com/health/index.php?cat=61 Latest Advances In Gene Research]
- [http://www.dnai.org DNA Interactive] (requires Macromedia Flash)
- [http://3dscience.com/3d_dna_models.asp Free 3d DNA model Images]
- [http://nist.rcsb.org/pdb/molecules/pdb23_1.html DNA: PDB molecule of the month]
- [http://www.fidelitysystems.com/Unlinked_DNA.html DNA under electron microscope]
- [http://www.myfirstbookaboutdna.com My First Book About DNA] Designed for children to learn more about DNA.
-
- [http://www.rotten.com/library/medicine/dna/ Rotten Library] articles on DNA
- Watson, James, and Francis Crick, "[http://biocrs.biomed.brown.edu/Books/Chapters/Ch%208/DH-Paper.html Molecular structure of nucleic acids], A structure for Deoxyribose Nucleic Acid". April 2, 1953. (paper on the structure of DNA) Category:Nucleic acids Category:Genetics
- ko:DNA ms:DNA ja:デオキシリボ核酸 simple:DNA th:ดีเอ็นเอ

Quiz Kids

Quiz Kids, a popular radio-TV series of the 1940s and 1950s, was created by Chicago public relations and advertising man Louis G. Cowan. Originally sponsored by Alka-Seltzer, the series was first broadcast on NBC from Chicago, June 28, 1940, airing as a summer replacement show for Alec Templeton Time. It continued on radio for the next 13 years. On television, the show was seen on NBC and CBS from July 6, 1949, to September 27, 1956. The premise involved host Joe Kelly asking questions sent in listeners and researched by Eliza Hickok. The answers were supplied by a panel of five children, chosen for their high IQs. The first Quiz Kid was six-year-old nature expert Gerard Darrow, and for the initial premiere panel, he was joined by Mary Ann Anderson, Joan Bishop, Cynthia Cline, Van Dyke Tiers and Charles Schwartz. Other Quiz Kids of the 1940s were Joan Alizier, Claude Brenner, Geraldine Hamburg, Mary Clare McHugh and math experts Joel Kupperman and Richard Williams. Panelists rotated throughout the 1940s, but they were no longer eligible to participate once they reached the age of 16. One of the notable Quiz Kids is the Nobel Prize-winning biologist James D. Watson. Others include actor and dialect coach Bob Easton, producer Harve Bennett and actress Vanessa Brown.

Listen to


- [http://www.richsamuels.com/nbcmm/quizkids/index.html The Quiz Kids (12/23/48)]

Reference


- Whatever Happened to the Quiz Kids? The Perils and Profits of Growing Up Gifted by Ruth Duskin Feldman (Chicago Review Press, 1982; reprinted by Backinprint.com, 2000)
- Quiz Kids and the Crazy Question Mystery by Carl Smith (Whitman, 1946)

University of Chicago

The University of Chicago is a private co-educational university located in Chicago, Illinois. Over a century old, it is renowned for its contributions to teaching and research, and recognized as one of the world's foremost research institutions. Known as the "teacher of teachers", scholars and researchers affiliated with the University of Chicago have earned more Nobel Prizes than any institution except Cambridge University. The academic home of leading intellectuals like Allan Bloom, Subrahmanyan Chandrasekhar, Ronald Coase, Milton Friedman, Richard Posner, and Leo Strauss, the University of Chicago is often considered to be among the most intellectual and rigorous of American universities.

Location and campus

The University is located eight miles (13 km) south of the Loop in the Chicago neighborhoods of Hyde Park and Woodlawn. The campus is noted for its English Collegiate Gothic architecture (carried out entirely in limestone); the buildings and layout of the Main Quadrangle have been deliberately patterned after Oxford and Cambridge from the founding of the University. Buildings that are more contemporary have attempted to complement the style of the original buildings with mixed success. One of the most striking buildings is the brutalist Regenstein Library. The campus is home to several significant buildings, including Bertram Goodhue's Rockefeller Memorial Chapel (notable for its solid stone construction), the Oriental Institute, and Frank Lloyd Wright's Robie House. The campus spans the Midway Plaisance, a large linear public park that was a part of the 1893 World's Columbian Exposition and designed by Frederick Law Olmsted. The bulk of the campus, including the main quadrangle and the hospitals, are north of the Midway; several of the professional schools are located south of the Midway. A recent $2 billion capital campaign has brought unprecedented expansion to the school. The last few years have featured much change on campus: the unveiling of Max Palevsky dormitory (primarily for first year students), the conversion of Bartlett Gym into a dining hall, the opening of the new Ratner Athletic Center (a César Pelli design) and matching parking/office structure, the construction of the new Comer Children's Hospital, the Graduate School of Business' new Hyde Park Center (a Rafael Viñoly building), and an Interdivisional Research Building for sciences. The University has also expanded outside of Hyde Park, opening a new the new Paris Center on the Left Bank (for collegiate study abroad). The University plans to direct the next stage of its “master plan” towards revamping and consolidating dormitories, many of which are far from campus and aging poorly. Plans are being prepared for the construction of a new undergraduate dormitory on land south of the Midway. The Graduate School of Business also maintains campuses in Singapore and London.

History

London London] London, located on the University's campus]] London] London The University was founded by John D. Rockefeller (of Standard Oil fame), at the end of a wave of university foundings stretching from the middle of the 19th century until the beginning of the 20th (Washington University in St. Louis, MIT, Vanderbilt, Johns Hopkins, University of Southern California, Stanford, Caltech, Northwestern, Rice University, and Carnegie Mellon also came into being during this time period). Incorporated in 1890, the University has always dated its founding as July 1, 1891, when William Rainey Harper became its first President. Westward migration, population growth, and the industrialization of America led to an increasing need for elite schools away from the East coast - schools whose focus would be on issues vital to national development. Rockefeller’s choice of Chicago – he was urged to build in the New England or the Mid-Atlantic States – demonstrated his outspoken desire to see Thomas Jefferson’s dream of a "natural aristocracy," determined by talent rather than familial heritage, rise to national prominence (he having pulled himself up by the figurative bootstraps). His early fiscal emphasis on the Physics department showed his pragmatic, yet nevertheless intellectually rigorous, desires for the school. Founded under Baptist auspices, the University today lacks a sectarian affiliation. The school's traditions of rigorous scholarship were established by Presidents William Rainey Harper and Robert Maynard Hutchins. Allowing women and minorities to matriculate from its inception, when their access to other leading Universities was an extreme rarity, the University counts among its alumni many prominent pioneers from both groups. Different from many other universities, the school was first set up around a number of graduate research institutions, following Germanic precedent. The College remained quite small (numerically and in intra-institutional importance) compared to its East coast peers until the middle of the twentieth century. As a result, graduate research and professional programs at the University continue to dwarf undergraduate education by a two-to-one student ratio (its undergraduate student body remains the third smallest amongst top 15 universities, behind historically small Dartmouth and Caltech). Nevertheless, most faculty members have dual appointments to their respective Schools, Divisions or Institutes, as well as to the undergraduate College. An important event in the development of nuclear energy took place at the university. On December 12, 1942 the world's first self-sustaining nuclear reaction was achieved at Stagg Field on the campus of the university under the direction of Enrico Fermi. A sculpture by Henry Moore marks the location where this reaction took place; the stadium has since been demolished to make way for the Regenstein Library.

Divisions and schools

The University currently maintains twelve units, grouped into divisions for graduate research, professional schools, the undergraduate College, the Library, the Press, the Lab Schools, and the Hospitals. The Divisions: Biological Sciences, Social Sciences, Physical Sciences, and Humanities, The Professional Schools: the Divinity School, the University of Chicago Law School, the Graduate School of Business, the Pritzker School of Medicine, the Harris School of Public Policy Studies and the School of Social Service Administration. The Graham School of General Studies is administrative rather than a formal school within the University, and administers a variety of degree and non-degree extension work for high school students through postgraduates. The University furthermore features the Laboratory Schools (day care through high school, founded by John Dewey and considered one of the leading preparatory schools in the United States), the Hyde Park Day Schools (ages 6-15, for the learning disabled of otherwise exceptional ability) and the Orthogenic School (a residential treatment program for ages 5-20 with behavioral and emotional problems). The University also administers two public charter schools on the South Side of Chicago, although these schools are not considered a true part of the University community (see also Argonne National Laboratory). The Princeton Review in 2004 rated the University as having the "Best Overall Educational Experience" for undergraduates among all American universities and colleges (the student-to-faculty ratio of 4:1, ranked the second lowest amongst top 50 American Universities, allows for small class sizes and exceptional faculty interaction). The University's professional schools also rank highly. The Graduate School of Business is consistently ranked by numerous publications [http://businessmajors.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=businessmajors&zu=http%3A%2F%2Fwww.bschool.com%2Fussbys.html] as part of the leading cohort of business schools. Likewise, the Law School ranks 6th [http://www.usnews.com/usnews/edu/grad/rankings/law/brief/lawrank_brief.php (US News)] and 2nd [http://www.utexas.edu/law/faculty/bleiter/rankings/rankings03.html (Leiter)], having received special accolades for its teaching quality (a distinction not given to other top ranked faculties), while the School of Social Service Administration School ranks 3rd [http://www.usnews.com/usnews/edu/grad/rankings/hea/brief/sow_brief.php (US News)]and 1st [http://www.socialpsychology.org/gsocwork.htm (Gourman Report)]. Moreover, the Divinity School ranks 2nd [http://www.phds.org/rankings/rank.php?d=9&w1=5&s1=1&w2=0&s2=1&w21=0&s21=-1&w0=5&s0=1&w6=5&s6=1&w7=0&s7=1&w4=0&s4=1&w3=0&s3=1&w13=0&s13=1&w15=0&s15=1&w5=0&s5=1&w19=0&s19=1&w20=0&s20=1&w14=0&s14=1&w16=0&s16=1&w17=0&s17=1&w18=0&s18=1&submit=Continue+%3E (National Research Council)], with the Pritzker School of Medicine ranking 19th [http://www.usnews.com/usnews/edu/grad/rankings/med/brief/mdrrank_brief.php (US News)]. The Irving B. Harris Graduate School of Public Policy Studies ranks 17th [http://www.usnews.com/usnews/edu/grad/rankings/pub/brief/pad_brief.php (US News)]. The University of Chicago Press is the largest university press in the country and publishes The Chicago Manual of Style, the definitive guide to American English usage. The University also operates a number of off-campus scientific research institutions, including membership in the Universities Research Association that opperates Fermilab, or the Fermi National Accelerator Laboratory, as well as Argonne National Laboratory, part of U.S. Department of Energy's national laboratory system. The University also owns and operates Yerkes Observatory in Williams Bay, Wisconsin, the Oriental Institute, and has a stake in Apache Point Observatory in Sunspot, New Mexico. The University is also a founding member of the Committee on Institutional Cooperation. The economics department is particularly well-known, so much so that an entire school of economics thought ("The Chicago School") bears its name. Characterized by conservative thinkers and Nobel Prize winners like Milton Friedman, George Stigler, Gary Becker and Robert Lucas, the department has played an important part in shaping thought on the efficacy of the free market. Rather infamously, Chicago economists, the "Chicago Boys", assisted Chilean dictator Augusto Pinochet in planning out his country's finances. The school is also known for the creation of the first Department of Sociology in the United States, which founded its own Chicago school of sociology. Scholars affiliated with this first school are considered widely important to the field and include Albion Small, George Herbert Mead, Robert E. Park, W. I. Thomas, and Ernest Burgess. The school's sociology program remains among the nation's highest ranked.

Sports and traditions

W. I. Thomas The school's sports teams are called the Maroons and their athletic colors are maroon and white. [http://athleti