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Wikipedia talk:Selected anniversaries/April 15

tank image
the image with the tanks took place in early June of 1989. the image should not be used for April 15. Kingturtle 08:26, 15 Apr 2004 (UTC)

 * And yet that photo of Jackie Robinson was taken after the event depicted on this page. --mav

 * Touche...but I see a difference between a portrait and an actual event. Portraits tend to be "timeless." But an image of historical context should be accurate date-wise. Kingturtle 16:33, 15 Apr 2004 (UTC)

Titanic
I think mention of the RMS Titanic belongs on April 15, not 14. The important part of the Titanic event happened on April 15 (meaning the actually sinking) The only actual significant part of the Titanic disaster that happened on April 14 was striking the iceberg MechBrowman 21:40, Apr 11, 2005 (UTC)

 * I think it's okay on either day, as long as the item is accurately worded. Hitting the iceberg was the critical starting point of the sinking, which took hours.  Anyway, a 5th item is needed for the SA template for April 14th, while the template for the 15th has 6 items, i.e. 1 too many.  Hence the move seems alright to me. ... However, for 2006, the bombing of Mumbai on April 14th, 1944 (See Wikipedia talk:Selected anniversaries/April 14.) may bump the Titanic item back to April 15th to avoid featuring 2 catastrophes on the same day .... How's that ? :-) -- PFHLai 16:21, 2005 Apr 13 (UTC)

 * Now that I thought about it, it doesn't matter too much since most people know what happens to Titanic after it hits the iceberg, but if April 15 ever has room (for whatever reason) Titanic should be moved back. MechBrowman 16:31, Apr 13, 2005 (UTC)

 * The item on boxing would probably be the first to go .... -- PFHLai 16:52, 2005 Apr 13 (UTC)

Jackie Robinson
"1947 - African American Jackie Robinson of the Brooklyn Dodgers broke the color line in professional baseball"

This was not the first time he played professional baseball (surely the Negro League was professional, not to mention the minor league). It was his debut in Major League Baseball. So I think that the quoted item should say Major League Baseball in place of professional baseball. DHR 18:44, 15 April 2006 (UTC)
 * I've edited the line for next year. Is it better now ? --PFHLai 05:20, 16 April 2006 (UTC)

 * "1947 - African American Jackie Robinson of the Brooklyn Dodgers played his first game in Major League Baseball, breaking the color line in professional baseball"
 * Thanks! Unfortunately, this still isn't right.  Surely the colour line in professional baseball was broken by or before Jackie Robinson played for the Montreal Royals 1946.  The Royals were a professional team and they were mostly white (unlike the Negro Leagues).  Again, replacing the remaining "professional baseball" with "Major League Baseball" would make this correct.  When claiming a first, it is important to make the claim accurate.  DHR 06:31, 17 April 2006 (UTC)
 * Hmmm.... "the color line in professional baseball" seems ill-defined. Let's avoid the debate on which color line being 'the' color line. I'm looking for a way to keep the link to Professional baseball, as that page actually has a paragraph about Robinson. How about "a key step towards racial desegregation in professional baseball" ? --PFHLai 07:26, 17 April 2006 (UTC)
 * Found a better page: Baseball color line. I've completely rewritten the line. How is it now ? -- PFHLai 07:39, 17 April 2006 (UTC)
 * "1947 - Jackie Robinson, the first African American to break the baseball color line, played his first game in Major League Baseball as a first baseman with the Brooklyn Dodgers"
 * Thanks again. Much better.  I think that it is correct but a bit misleading.  It might be improved as "1947 - Jackie Robinson, the first African American to break the baseball color line, became the first African American to play in Major League Baseball on this date."  This is still awkward.  The problem is that the second portion justifies the anniversary (first in MLB) but the first part has the link to the relevant article (baseball color line).  Another thought: "1947 - Jackie Robinson became the first African American to play in Major League Baseball (see the baseball color line)".  Details can be added to taste (I'm trying to be concise). DHR 02:03, 18 April 2006 (UTC)
 * Can we avoid the brackets ? Let me think .... -- PFHLai 05:07, 18 April 2006 (UTC)

Hillsborough Disaster
All the guidelines and the FAQ above are noted ... nevertheless the omission from the OTD list of the Hillsborough Disaster, on the 20th anniversary thereof and when it is featured in retrospective news and opinion articles worldwide, is hard to understand. Darcyj (talk) 08:47, 15 April 2009 (UTC)
 * I second that. Madcynic (talk) 11:21, 15 April 2009 (UTC)
 * Sorry, forgot that Hillsborough Stadium could have been bolded as the alternative selected article. Cheers. Zzyzx11 (talk) 20:21, 15 April 2009 (UTC)
 * Thirded. A story about McDonald's opening a ninth store? Really? I know that the OTD decisions aren't based on importance/signifance but it seems slightly wrong... It's Malpass 93! (drop me a ___) 15:47, 15 April 2011 (UTC)

Walter O'Malley vs. Jackie Robinson
With the addition of this edit and the accompanying hidden comment, I'm kinda of concerned if we did have to choose between one or the other. If both articles are equal in terms of the "well-written article" criterion, it seems to me there might be more complaints from baseball fans if O'Malley was chosen ahead of Robinson. Yes, I know that Robinson has been posted here for 5+ years, but from what I have read about baseball, there was an extremely notable reason why, among others, Robinson's jersey number, 42, was retired by every Major League Baseball team in 1997 – and that breaking the color barrier seemed to have much more impact to the sport than expanding to the West Coast. Cheers. Zzyzx11 (talk) 02:47, 30 March 2010 (UTC)

No Lincoln?
No Lincoln assassination in "on this day"? —Preceding unsigned comment added by Kenn5 (talk • contribs) 09:06, 15 April 2010 (UTC)
 * Yes, its true that Lincoln died on April 15. But the Assassination of Abraham Lincoln itself, when John Wilkes Booth's gun actually went off, happened on April 14. Zzyzx11 (talk) 10:50, 15 April 2010 (UTC)

2012 notes
— howcheng  {chat} 11:22, 15 April 2012 (UTC)
 * Moved to Ineligible: 1936–1939 Arab revolt in Palestine (maintenance); Walter O'Malley (date not found in article)
 * Omitted: Serse (ineligible—maintenance); A Dictionary of the English Language; Sinking of the RMS Titanic (TFA for 2012); Jackie Robinson; McDonald's; World Trade Organization
 * Included: Shimabara Rebellion (first appearance); I Wandered Lonely as a Cloud (first appearance); Great Mississippi Flood of 1927 (first appearance); Boeing B-52 Stratofortress (2nd appearance, last in 2010); Hu Yaobang (2nd appearance, last in 2008; rescued from Ineligible)

2013 notes
— howcheng  {chat} 05:16, 14 April 2013 (UTC)
 * New articles (unused): Teapot Dome scandal
 * Omitted: William Wordsworth/I Wandered Lonely as a Cloud; Great Mississippi Flood of 1927; Boeing B-52 Stratofortress; Hu Yaobang
 * Included: Kim Il-sung (rescued from Ineligible); Lateran Council (769) (first appearance); Siege of Bari (first appearance); A Dictionary of the English Language (8th appearance, last in 2011); Jackie Robinson (8th appearance, last in 2011); Hillsborough disaster (5th appearance, last in 2007)
 * Repeats: Shimabara Rebellion (2nd consecutive appearance, 2 total; 375th anniversary)
 * Addendum: Shimabara Rebellion later removed for balance. — howcheng  {chat} 22:59, 15 April 2013 (UTC)

2014 notes
— howcheng  {chat} 03:44, 14 April 2014 (UTC)
 * Moved to Ineligible: Boeing B-52 Stratofortress (maintenance); McDonald's (maintenance)
 * Rescued from Ineligible (unused): 1986 United States bombing of Libya
 * New articles (unused): Boston Marathon bombings
 * Omitted: Lateran Council (769); Siege of Bari; A Dictionary of the English Language (ineligible—maintenance); Jackie Robinson
 * Included: Tax Day (rescued from Ineligible); Shimabara Rebellion (2nd appearance, last in 2012); William Wordsworth/I Wandered Lonely as a Cloud (both: 2nd appearance, last in 2012); Walter O'Malley (first appearance; rescued from Ineligible); World Trade Organization (7th appearance, last in 2011)
 * Repeats: Hillsborough disaster (2nd consecutive appearance, 6 total; 25th anniversary)

2015 notes
— howcheng  {chat} 11:22, 13 April 2015 (UTC)
 * Rescued from Ineligible (unused): Serse; A Dictionary of the English Language
 * Omitted: William Wordsworth/Dorothy Wordsworth/I Wandered Lonely as a Cloud; Walter O'Malley; Hillsborough disaster
 * Included: Siege of Bari (2nd appearance, last in 2013); RMS Titanic/Sinking of the RMS Titanic (Titanic: 10th appearance, last in 2012; Sinking: first appearance); 1986 United States bombing of Libya (4th appearance, last in 2008)
 * Repeats: Shimabara Rebellion (2nd consecutive appearance, 3 total); World Trade Organization (2nd consecutive appearance, 8 total; 20th anniversary)
 * Note: Boston Marathon bombings remained unused as it is currently in ITN due to the trial.

Checking the list

 * Boeing B-52 Stratofortress was listed in ineligible list because of needing expansion which is I think resolved by now. It has appeared two times on the main page in the On this day box. --Mhhossein (talk) 13:57, 12 April 2016 (UTC)

 * I found no problem with articles in eligible list. Mhhossein (talk) 14:30, 12 April 2016 (UTC)
 * 1986 United States bombing of Libya, which appeared on the main page last year, has reference issues and was crossed out of eligible list. I suggest to include Teapot Dome scandal which has apparently never been on the main page. Mhhossein (talk) 05:56, 13 April 2016 (UTC)

Titanic - 2
''1912 – The passenger liner 'RMS Titanic sank (pictured) about two hours and forty minutes after colliding with an iceberg, killing more than 1,500 people.
 * – Quibble with sentence structure: The above can be understood as saying that 1,500 died in the collision with the iceberg. Suggested rewording:
 * "The ocean liner RMS Titanic sank (pictured) about two hours and forty minutes after colliding with an iceberg, and more than 1,500 people died from drowning or exposure." Sca (talk) 14:51, 12 April 2016 (UTC)
 * How about it: "The ocean liner RMS Titanic ...., the event left more than 1,500 people dead."? Mhhossein (talk) 05:31, 13 April 2016 (UTC)
 * Or "...iceberg, as a result of which..." – or "...iceberg, resulting in the deaths of ...." Sca (talk) 14:48, 14 April 2016 (UTC)

2016 notes
— howcheng  {chat} 06:30, 13 April 2016 (UTC)
 * Omitted: Siege of Bari; RMS Titanic/Sinking of the RMS Titanic; 1986 United States bombing of Libya (ineligible—maintenance); World Trade Organization
 * Included: Lateran Council (769) (2nd appearance, last in 2013); Serse (5th appearance, last in 2011); Teapot Dome scandal (first appearance); Boston Marathon bombing (first appearance)
 * Repeats: Shimabara Rebellion (3rd consecutive appearance, 4 total)
 * Howcheng: Jackie Robinson blurb will have its 70th anniversary next year. Does it matter? Mhhossein (talk) 07:03, 13 April 2016 (UTC)
 * Yes, he'll go in for sure next year, unless he's TFA or POTD. Round-number anniversaries usually get priority. — howcheng  {chat} 15:47, 13 April 2016 (UTC)

2017 notes
— howcheng  {chat} 17:38, 15 April 2017 (UTC)
 * Moved to Ineligible: A Dictionary of the English Language (maintenance); Hu Yaobang (maintenance)
 * Rescued from Ineligible (unused): Boeing B-52 Stratofortress
 * Omitted: Father Damien (ineligible—maintenance); Lateran Council (769); Shimabara Rebellion; Serse; Teapot Dome scandal (ineligible—maintenance); Boston Marathon bombing
 * Included: I Wandered Lonely as a Cloud (3rd appearance, last in 2014; blurb also previously featured William Wordsworth, which is now ineligible); Great Mississippi Flood of 1927 (2nd appearance, last in 2012; 90th anniversary); Jackie Robinson (9th appearance, last in 2012; 70th anniversary); Hillsborough disaster (7th appearance, last in 2014); Leonardo da Vinci (first appearance); Leonhard Euler (first appearance); Greta Garbo (first appearance)

2018 notes
— howcheng  {chat} 03:40, 15 April 2018 (UTC)
 * New articles (unused): 2001 Bangladesh–India border clashes (moved from April 16)
 * Omitted: I Wandered Lonely as a Cloud; Great Mississippi Flood of 1927; Jackie Robinson; Hillsborough disaster; Leonardo da Vinci; Leonhard Euler; Greta Garbo
 * Included: Shimabara Rebellion (5th appearance, last in 2016); Serse (6th appearance, last in 2016); 1936 Tulkarm shooting (first appearance); Walter O'Malley (2nd appearance, last in 2014; 60th anniversary); World Trade Organization (9th appearance, last in 2015); Guru Arjan (first appearance); Mikhail Lomonosov (first appearance); Emma Watson (first appearance)

2019 notes
— howcheng  {chat} 16:58, 15 April 2019 (UTC)
 * Omitted: Shimabara Rebellion; Serse; 1936 Tulkarm shooting; Walter O'Malley; World Trade Organization; Guru Arjan; Mikhail Lomonosov; Emma Watson
 * Included: Lateran Council (769) (3rd appearance, last in 2016; 1250th anniversary); Sinking of the RMS Titanic (2nd appearance, last in 2015); Boeing B-52 Stratofortress (3rd appearance, last in 2012); Hillsborough disaster (8th appearance, last in 2017; 30th anniversary); Richard Poore (first appearance); Wilhelm Busch (first appearance); Arsenio Lacson (first appearance)

2020 notes
— howcheng  {chat} 20:44, 16 April 2020 (UTC)
 * New articles (unused): George Calvert, 1st Baron Baltimore; Richard von Weizsäcker; Claudia Cardinale; Hugh Thompson Jr.; Dara Torres; Milton Bradley (baseball); Seth Rogen
 * Omitted: Lateran Council (769); Sinking of the RMS Titanic; Boeing B-52 Stratofortress; Hillsborough disaster; Richard Poore; Wilhelm Busch; Arsenio Lacson
 * Included: Siege of Bari (3rd appearance, last in 2015); I Wandered Lonely as a Cloud (4th appearance, last in 2017); World Trade Organization (10th appearance, last in 2018); Notre-Dame de Paris fire (first appearance); Robert Persons (first appearance); Stanley Bruce (first appearance); Greta Garbo (2nd appearance, last in 2017; 30th anniversary)

2021 notes
— howcheng  {chat} 07:20, 17 April 2021 (UTC)
 * Deleted: 2001 Bangladesh–India border clashes (moved back to April 16)
 * Moved to Ineligible: Sinking of the RMS Titanic (Frederick Fleet is POTD for 2021-04-14)
 * New articles (ineligible): Carol W. Greider (POTD for 2021)
 * New articles (unused): Robert W. Gore
 * Omitted: Siege of Bari; I Wandered Lonely as a Cloud; World Trade Organization; Notre-Dame de Paris fire; Robert Persons;Stanley Bruce; Greta Garbo
 * Included: Shimabara Rebellion (6th appearance, last in 2018); Serse (7th appearance, last in 2018); 1936 Tulkarm shooting (2nd appearance, last in 2018); Walter O'Malley (3rd appearance, last in 2018); George Calvert, 1st Baron Baltimore (first appearance); Richard von Weizsäcker (first appearance); Dara Torres (first appearance)

2022 notes
— howcheng  {chat} 03:17, 16 April 2022 (UTC)
 * Rescued from Ineligible (unused): Carol W. Greider
 * Omitted: Shimabara Rebellion; Serse; 1936 Tulkarm shooting; Walter O'Malley; George Calvert, 1st Baron Baltimore; Richard von Weizsäcker; Dara Torres
 * Included: Lateran Council (769) (4th appearance, last in 2019); Battle of Rain (first appearance); Sinking of the RMS Titanic (3rd appearance, last in 2019; rescued from Ineligible); Teapot Dome scandal (2nd appearance, last in 2016; 100th anniversary; rescued from Ineligible); Boeing B-52 Stratofortress (4th appearance, last in 2019; 70th anniversary); Leonhard Euler (3rd appearance, last in 2017); Arsenio Lacson (2nd appearance, last in 2019; 60th anniversary); Seth Rogen (first appearance; 40th birthday)


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Guarneri Quartet

The Guarneri Quartet was an American string quartet founded in 1964 at the Marlboro Music School and Festival. It was admired for its rich, warm, complex tone and its bold, dramatic interpretations of the quartet literature, with a particular affinity for the works of Beethoven and Bartók. Through teaching at Harpur College (which became Binghamton University), University of Maryland, Curtis Institute of Music, and at Marlboro, the Guarneri players helped nurture interest in quartet playing for a generation of young musicians. The group's extensive touring and recording activities, coupled with its outreach efforts to engage audiences, contributed to the rapid growth in the popularity of chamber music during the 1970s and 1980s. The quartet is notable for its longevity: the group performed for 45 years with only one personnel change, when cellist David Soyer retired in 2001 and was replaced by his student Peter Wiley. The Guarneri Quartet disbanded in 2009.

Musicians
1st violin
 * Arnold Steinhardt (b. Los Angeles, 1 April 1937) Steinhardt is the elder of two sons born to music-loving Polish parents. He began studying the violin at age 6, and when he was 17 he entered Curtis Institute of Music in Philadelphia as a pupil of Ivan Galamian. Prior to the founding of the Guarneri Quartet, Steinhardt spent four years as assistant concertmaster of the Cleveland Orchestra under George Szell; he spent summers at the Marlboro Music Festival and in 1962 he studied in Switzerland with Joseph Szigeti.

 * Steinhardt is 6 feet 3 inches tall, and as a result he has unusually long arms, which has made it necessary to adjust his playing posture to avoid pain. He is outgoing and articulate, and has written two books. When touring with the quartet, he liked to browse in antique shops, and he particularly collected old locks. Since the Guarneri’s dissolution he has maintained a blog containing his personal reflections and reminiscences (see External links).

2nd violin
 * John Dalley (b. Madison, Wisconsin, 1 June 1936) Dalley’s parents were both musicians, and he started violin lessons at the age of 4. He spent summers at Interlochen National Music Camp, and in his teens he went to Tuscaloosa to study at the University of Alabama with Ottokar Čadek. At 18, he enrolled at Curtis Institute, working with Efrem Zimbalist. Following graduation from Curtis, Dalley taught at Oberlin Conservatory of Music, and later played alongside David Soyer in a group known as the American String Quartet.

 * Dalley is thoughtful and affable, with a dry wit and occasional bursts of outright clowning; but he was the most introverted of the Guarneri musicians, often skipping post-concert social events and disappearing immediately after a concert. Dalley is a skilled maker of bows for stringed instruments; he would sometimes carry the necessary equipment on the road, so that he could work on a bow in his hotel room, while the others might be attending a reception following a performance.

Viola
 * Michael Tree (b. Newark NJ, 19 Feb 1935; d. New York, 30 Mar 2018) Tree was the son of Samuel Applebaum, a respected violin teacher and the author of several books on technique. He started lessons with his father at age 5, and entered Curtis Institute at the unusually young age of 12. He studied with Leah Luboshutz, Veda Reynolds, and ultimately with Efrem Zimbalist. Following his graduation, Tree made a successful debut at Carnegie Hall and toured internationally as a violin soloist, playing with a number of orchestras. In 1959 he began spending summers at Marlboro, where he met David Soyer and played with him and pianist Anton Kuerti in a group known as the Marlboro Trio.

 * Tree was described by Steinhardt as an efficient problem solver, and as "one part musician, one part cutup", always ready to relieve an overly-intense moment with a joke or some kind of buffoonery. He was the most high-strung member of the quartet, particularly prone to nervousness before performances. An avid tennis player, he liked to play with local experts or with friends while on tour.

Violoncello (1964–2001)
 * David Soyer (b. Philadelphia, 24 Feb 1923; d. New York, 25 Feb 2010) Soyer was, by about 12 years, the oldest of the original members of the quartet, and his pre-Guarneri experience was more extensive. The only one in the group who was not trained at Curtis, Soyer studied cello with Diran Alexanian, Emanuel Feuermann, and Pablo Casals. During World War II, he played euphonium in the United States Navy Band. Following the war, he played cello as a member of the NBC Symphony Orchestra under Arturo Toscanini, Columbia Symphony Orchestra, the Ed Sullivan Show orchestra, and various groups that recorded jingles and commercials. He played with several chamber music ensembles before the Guarneri:  the Guilet and New Music Quartets, the short-lived American Quartet with John Dalley, and  the Marlboro Trio with Michael Tree and Anton Kuerti.

 * In rehearsals, Soyer was outspoken and forceful; Steinhardt describes him as "blunt and highly opinionated". Soyer considered that his experiences performing commercial music helped him grow as an artist, and firmly believed that young musicians should be exposed to dance music, folk music, and gypsy fiddling. He was a connoisseur of art, and an avid sailor who owned a 24-foot sloop.

Violoncello (2001–2009)
 * Peter Wiley (b. Utica NY, 1955) Wiley grew up in central New York State, and at age 11, he started cello lessons with David Soyer during the time the Guarneri Quartet was in residence at Harpur College in Binghamton. When Soyer joined the faculty of Curtis Institute in 1968, Wiley enrolled there and continued his cello studies. Graduating in 1974, he played with the Pittsburgh Symphony and the Cincinnati Symphony before joining the Beaux Arts Trio to replace retiring cellist Bernard Greenhouse. He left the Beaux Arts in 1998 to co-found the Opus One Piano Quartet. When Soyer retired from the Guarneri in 2001, Wiley was quickly and unanimously chosen to succeed his mentor.

Instruments
Despite the group's name, only one instrument made by the celebrated Guarneri family of Cremona was played for any significant time by a member of the quartet: for many years David Soyer used an Andrea Guarneri cello made in 1669. He later switched to a Gagliano cello made in Naples in 1778. After trying several violins (including a Guarneri), Steinhardt settled on a Cremona instrument made by Lorenzo Storioni in the late 18th century. Dalley plays a French violin made in 1810 by Nicholas Lupot. In the quartet's early years Tree played a viola (patterned after Andrea Guarneri's "Conte Vitale") made by Harvey Fairbanks, a luthier from Binghamton, New York. Later, his primary instrument became a 1750 viola made by Dominicus Busan of Venice; he also plays a modern instrument made by Hiroshi Iizuka. Wiley plays a cello made around 1700 by Matteo Goffriller of Venice.

At one point in the mid-1990s the quartet was offered the extended loan of a set of four rare Stradivarius instruments owned by the Corcoran Gallery in Washington, D.C. After considering the offer, the Guarneri musicians declined, preferring to play the instruments each had chosen for himself. Steinhardt has compared the task of finding a violin well matched to a performer's style to that of finding a spouse, and he adds, "After much trial and error, each of us has found what could aptly be called his musical soul mate."

History and activities
Steinhardt, Dalley, Tree and Soyer coalesced into the Guarneri Quartet at the Marlboro Music School and Festival in Marlboro VT, where all of them spent summers during the early 1960s. During the summers of 1962 and 1963, the four played chamber music together in various permutations, and with encouragement from Festival director Rudolf Serkin and from Alexander Schneider (second violinist of the Budapest String Quartet) the new quartet was launched on 20 July 1964 with a concert at Nantucket, Massachusetts. The name Guarneri was suggested by Boris Kroyt (violist of the Budapest String Quartet), who had played with a short-lived group of that name in Germany before World War II.

In the fall of 1964, the quartet began a four-year residency at Harpur College (now known as Binghamton University) in Binghamton, New York, where they taught advanced students, held a series of open rehearsals, and played 15 public concerts per year. Steinardt relates that the group found the situation attractive because Binghamton was within driving distance of their base in New York City, and it would provide an opportunity to rapidly build a repertoire, gain performing experience, and develop working relationships among themselves.

The Guarneri's New York City debut took place on 28 February 1965 at the New School for Social Research as part of a concert series arranged by Alexander Schneider. The enthusiastic audience included Fritz Steinway, of the concert management firm Judson, O’Neill, Beall and Steinway (which would shortly become the group's manager) and Max Wilcox, a record producer for RCA Victor, who quickly secured a recording contract for the Guarneri. Soon afterward, the group replaced the retiring Budapest String Quartet in a series of concerts at the Metropolitan Museum of Arta series that extended across the Guarneri's lifespan, ending only when the quartet disbanded in 2009. They appeared at the Mostly Mozart Festival beginning in 1966, and an ongoing series at Lincoln Center's Alice Tully Hall began in 1975. Other frequent New York venues included the Frick Collection, the 92nd Street Y, Rockefeller University and Washington Irving High School.

The Guarneri began touring almost immediately, with a concert in Cleveland on 20 April 1965. In the summer of that year they embarked upon their first European tour, performing in Geneva, Basel, Amsterdam, Cologne, and at the Festival of Two Worlds in Spoleto, Italy. As the quartet's reputation grew, both domestic and international tours became a way of lifeoften a grueling one. In the early years they played as many as 130 concerts per year, although by the 1980s they were attemptingnot always successfullyto limit their appearances to 100 per year.

While the members of the quartet unanimously and emphatically preferred live performances to studio recordings, they were, from the beginning, prolific recording artists. Their first session for RCA Victor took place in June 1965, and included quartets by Mozart, Dvořák and Mendelssohn. By 1998 the Guarneri's catalog exceeded 50 LPs and CDs, including numerous recordings with pianist Arthur Rubenstein. A partial discography can be found below.

The Guarneri musicians were active in teaching throughout the quartet's life. The affiliation with Harpur College continued until 1968, and in that year Steinhardt, Tree and Soyer were appointed to the faculty of the Curtis Institute of Music in Philadelphia. The members continued summer teaching at Marlboro, and in 1983, all four were appointed artists-in-residence at the University of Maryland at College Park, where they continued teaching up to and beyond the formal dissolution of the Guarneri Quartet in 2009.

David Soyer, who was about a dozen years older than his colleagues, retired in 2001, and his place was taken by Peter Wiley, Soyer's former student. The transition was symbolized in a Carnegie Hall concert that year, in which the Guarneri performed the Beethoven Quartet in B-flat major, op. 130, with Soyer playing cello, followed by the String Quintet in C by Schubert, with Soyer and Wiley taking the two cello parts. The incorporation of Wiley as cellist was a smooth one: "I don't feel like the new guy," he remarked. "I was a fan of the quartet since I was 11 years old…It was a very natural transition for me." Dalley added "It was actually very good for us when Peter came in, even though the quartet field was new to him…I think I learned more from Peter than he learned from us. He had a lot of good ideas that were brand new to us."

The members of the quartet decided to disband at the end of the 2009 season, with the intention of going out on a high note. Steinhardt remarked on the difficulty of their work, and added "We all had the sense that we're still playing pretty well, and it's better to quit at that point than to go past our time. We had surprisingly little discussion; everybody came to that conclusion rather quickly." Critics agreed that it was time to bow out; while still praising the Guarneri's tone and style, they perceived increasing technical imperfections and a decrease in the intensity of the group's emotional connection with the music. For some of the final concerts, David Soyer rejoined the Guarneri as the group once again played the Schubert Quintet in C, which is scored for two cellos.

David Soyer died on 25 February 2010, and Michael Tree died on 30 March 2018. As of 2018, the other Guarneri musicians continue to teach and perform under their own names.

Musical style and repertoire
The Guarneri's musical style was distinctive and widely admired. It has been described as "suave, elegant, highly nuanced, technically flawless", as "lush and vibrant sound married to an intensity of purpose", and as "seamless, warm and impassioned playing [with] a unanimity that did not efface individual personalities." Philadelphia critic Daniel Patrick Stearns remarked that: Audiences kept coming back for the warmth of tone that was built from the inside out, with an unusually strong presence from second violin and viola, but with soft attacks and releases. Steinhardt's leaner tone defined that cloud of sound with a laserlike precision.

The quartet took a dramatic, even rambunctious approach to performing music; Steinhardt called it "swashbuckling and boisterous" when contrasting it with the Orion String Quartet, whose style he admiringly described as "refined and thoughtful." In another context he stated that "our top priority is to try and deliver the essence of the music and create goosebumpsgive a performance that will be as memorable and vital and energetic as possible. I'd like to think we set caution slightly to the side in favor of emotional impact." The high-voltage performance style mellowed somewhat as the group matured; in a 2009 review of the quartet's performance of Beethoven's Quartet in E-flat, op. 127, Oregon critic David Stabler reported: Instead of the feel of discovery, freshness and unpredictability, we heard more tempered playing. Instead of sharpness and strength in the opening of the E-Flat Quartet, the soft-pedaled sounds suggested a different way of engaging with the music. Less about surprise and urgency, more about knowing and acceptance. For the Guarneri, it was ground well trodden.

Many quartets strive to present a clean and cohesive tone, working to coordinate phrasing, bowing and intonation so as to create the sense of a single instrument with four registers. David Blum notes that the Guarneri explicitly followed a different path: They readily admit that other quartets look for and achieve a more consistent blend of timbre and unity of style. They enter into the music’s expressive stream and let it work upon them, even if, in so doing, an occasional rough edge appears. Their goal is always to communicate the music as a living experience. In a similar vein, Dalley expressed the Guarneri musicians’ intent as follows: [Y]ou heard four individual voices rather than four people trying to play alike. We liked to stand out individually in the quartet rather than play in a unified way. We wanted to have our own personalities come through rather than be submissive. Tree agreed: I think in view of many of our colleagues we'll be best known for never making a fuss about playing the same bowings. Some players would come backstage and wonder if we were fighting, because our bowings were different. We were unorthodox from the beginning, having a strong notion that we should play as best we can individually in our own comfort zone in terms of bowings and fingerings and so forth.

In its early years, the Guarneri's repertoire focused primarily on music of 18th and 19th century composers, and they became particularly known for their interpretations of Beethoven’s quartets. However, by the 1980s the quartet was incorporating more music from the 20th century in its programs. The musicians took a selective approach to modern musicthey were not enthusiastic about what Tree called "very experimental, avant-garde music" and they had mixed feelings about Schoenberg and Shostakovich but they became champions of the quartets of Bartók and their repertoire eventually included music by Webern, Berg, Stravinsky, Vincent Persichetti, Paul Hindemith, Witold Lutosławski, Hans Werner Henze, Leon Kirchner, and William Klenz. Several original compositions were written for the group, by Ned Rorem, Lukas Foss, Mario Davidovsky, and Richard Danielpour. The group also made a point of performing seldom-heard quartets by earlier composers, including those of Jean Sibelius, Leoš Janáček, Zoltán Kodály, and Juan Crisóstomo de Arriaga.

Group dynamics
Unlike most performing ensembles, the Guarneri permitted, and even encouraged, public awareness of their work as they prepared concerts, and they allowed backstage glimpses of the interpersonal dynamics within the group. From the beginning they conducted "genuine" open rehearsals, in which audiences could listen as they argued over the best way to play a passage or whether a piece they were considering ought to become part of their repertoire. They frequently held interactive sessions with audiences and they regularly made themselves available for interviews by journalists and writers. On several occasions they allowed observers to travel with the quartet and to publish detailed accounts of their activities onstage, in rehearsal, and during their travel time and free hours. In addition, Arnold Steinhardt published a book of memoirs in 1998 under the title Indivisible by Four: A String Quartet in Search of Harmony (see Resources). As a result of all this, a good deal is known about the way the group worked, musically and psychologically.

From the beginning, the Guarneri members rejected the then-common notion that the first violinist was the leader of the ensemble. The group insisted that all of the players were equals, and as a symbol of this, determined that whenever a piece called for one violin (for example, a piano quartet), second violinist John Dalley would play that part unless he chose not to do so. Similarly, all decisions were to be made by the group as a wholeand since four is an even number, that stance guaranteed a great deal of discussion when two members favored one option and two others preferred a different one. Dalley expressed the group's position as follows:"You have to be able to bend or give up some of your ideas. If you don't compensate and give in and compromise, you just don't get along. I think we had four strong personalities, and that's good. It's one way for a quartet to mature. The other way is to have a dictator who rules over the other three. That's the way it was in Europe, but Americans don't like that. It works faster, but the democratic way is more satisfying."

Thus the Guarneri's rehearsals were marked by vigorous give-and-take, with disagreements frequent and forcefully expressed. No point was too small for debate: in musical notation, a dot over a note means that it should be played staccato, and Steinhardt describes one public rehearsal in which the group argued for 20 minutes over precisely how much shortening one particular staccato-marked note ought to have. In general majority opinions prevailed, but a minority voice was listened to, and occasionally when one member had extremely strong feelings on a matter, he was allowed veto power. When the group's decision process hit a deadlock, they would sometimes play the passage one way for a Monday concert and a different way on Tuesday. The players came to accept and expect the constant flow of criticism without resentment, and the rehearsals were also laced with friendly banter and corny jokes. But praise was almost never expressed; Steinhardt describes the Guarneri as a "compliment-free zone," noting that this reduced competitiveness and eliminated any pressure to offer congratulations in return.

However, the frequency and intensity with which the players had to work together forced them to adopt measures to preserve their individual identities and maintain some degree of personal privacy. They seldom socialized outside of concert-related events, and while touring they often made independent travel and hotel arrangements. They would frequently split up during off days while on tour, and consciously avoided asking about the activities of the others. The musicians maintained a firewall between the quartet's activities and their family lives, and summers were protected as Guarneri-free time.

The devices the players used to resolve problems and maintain their personal privacy, combined with their genuine fondness for each other and for the music they played, made possible an unusually long life for the quartet. The four original musicians performed together for 37 consecutive years, "a remarkable record of longevity for a string quartet, in which tensions over music making, money and personal differences often cause breakups." After Soyer retired, the group continued, with Wiley playing cello, for another 8 years, bringing the Guarneri's total life to 45 years with only one personnel change. The quartet's longevity, along with the readily-available material about the group's interpersonal dynamics, has made it possible for the Guarneri to be used as a model in studies and pedagogy regarding collaborative leadership.

Cultural impact
There were only about a dozen American string quartets in 1964 when the Guarneri was born. Just 16 years later, there were over 250. While that growth cannot be attributed to any single cause, the Guarneri is frequently cited as a significant force assisting the boom. For one thing, the members’ active work as teachers increased student interest in playing string quartets. One need look no further than Peter Wiley, who began his cello studies with Soyer, to see an example. The group's teaching at Harpur, at University of Maryland, and particularly at Marlboro and Curtis certainly helped young musicians to develop an appetite for quartet music. James Reel quotes a Curtis student's thoughts: "There was always an excitement in the air at Curtis when they were about to show up," recalls Lucy Chapman Stoltzman, who studied particularly with Steinhardt, often in lessons lasting more than two hours…"It was the pure beauty of their sound and legato, and the sense of the inner voices was so strong, the sense of every voice being important in the way you want it to be," she says. "The Guarneri brought it to some new level that I hadn't heard before."

Another way in which the Guarneri facilitated the growth of interest in playing chamber music was through the example they set. In the early 1960s, music students aspired primarily to careers as soloists or orchestral musicians. The four Guarneri players took a substantial financial risk by establishing themselves as a professional string quartet in the absence of bookings, recording contracts, concert management, or even certainty of sufficient public interest. In the wake of their success, however, other musicians have been able to launch new quartets with more confidence that they can make a living playing chamber music, and by commanding significant fees, the Guarneri raised the payment baseline for all string quartets.

Finally, the Guarneri helped to build public awareness of chamber music, and thus increase demand for it. Their eagerness to communicate with their audiences, their interviews, open rehearsals, question-and-answer sessions all helped to make string quartets less esoteric, more familiar to listeners. Helen Drees Ruttencutter put it this way: They are said to have done for quartet music in America what Leonard Bernstein did for symphonic music – made it accessible and appealing to everyone open to a new musical experience. Audiences get a quadruple dose of what many managers consider one of the most important elements for a career in music: charisma. They have been hailed all over the world as "the Great American Quartet of the era" and "the greatest string quartet in the world."

Recordings
The Guarneri String Quartet has made numerous recordings during its long history, including some of the most important works in the string quartet and chamber music literature. They recorded for Arabesque, RCA Victor Red Seal, Philips and Surroundedby Entertainment. All recordings are with David Soyer as cellist unless it is noted that the cellist is Peter Wiley. A partial discography includes:

 * Juan Crisóstomo Arriaga – Complete String Quartets
 * Béla Bartók – Complete String Quartets
 * Ludwig van Beethoven – Complete String Quartets (recorded twice: on RCA and Philips), String Quintet in C Op. 29 (with Pinchas Zukerman)
 * Alexander Borodin – String Quartet No. 2
 * Johannes Brahms – Complete String Quartets, Complete String Quintets (with Pinchas Zukerman), Piano Quintet in f Op. 34 (with Arthur Rubinstein on RCA, with Peter Serkin on Philips), Complete Piano Quartets (with Arthur Rubinstein),
 * Claude Debussy – String Quartet (recorded twice: on RCA and on Surroundedby Entertainment)
 * Ernő Dohnányi – String Quartet No. 2 in Db (recorded twice: on RCA in 1980 and on Sony in 2009 with cellist Peter Wiley), String Quartet No. 3 in A (with cellist Peter Wiley)
 * Antonín Dvořák – Piano Quintet No. 2 Op. 81 (with Arthur Rubinstein), Quartet in C Op. 61, in F Op. 96 ("American"), in G Op. 106, in Ab Op. 105, Viola Quintet in Eb Op. 97 (with Walter Trampler), Terzetto Op. 74
 * Gabriel Fauré – String Quartet Op. 121 (recorded twice: on RCA and Surroundedby Entertainment), Piano Quartet in c Op. 15 (with Arthur Rubinstein)
 * Edvard Grieg – String Quartet in g Op. 27 (recorded twice: on RCA and Philips)
 * Joseph Haydn – String Quartets in D Op. 20 No. 4, in g Op. 74 No. 3, in G Op. 77 No. 1, in F Op. 77 No. 2
 * Hans Werner Henze – Piano Quintet (with Peter Serkin)
 * Leoš Janáček – Complete String Quartets
 * Zoltán Kodály - Quartet for Strings no 2, Op. 10 (with cellist Peter Wiley)
 * Felix Mendelssohn – String Quartet in an Op. 13, String Quartet in D Op. 44 No. 1, Viola Quintet in Bb Op. 87 (with Pinchas Zukerman), Octet in Eb Op. 20 (with the Orion String Quartet)
 * Wolfgang Amadeus Mozart – The Complete Piano Quartets (with Arthur Rubinstein), Eine kleine Nachtmusik (with Julius Levine), 6 String Quartets dedicated to Joseph Haydn (recorded twice: for RCA and Philips) (in G K387, in d K421, in E K428, in Bb K458, in A K464, in C K465), String Quartet in D K499, String Quartet in D K575, String Quartet in Bb K589, String Quartet in F K590, The Complete Viola Quintets (with Ida Kavafian, Steven Tenenbom, and Kim Kashkashian)
 * Maurice Ravel – String Quartet (recorded twice: for RCA and Surroundedby Entertainment)
 * Franz Schubert – String Quartets in a D804 (recorded twice: for RCA and Arabesque), in c "Quartettsatz", in d D810 "Death and the Maiden" (recorded twice: for RCA and Arabesque), in G D887, String Quintet in C D956 (with Leonard Rose), "Trout" Quintet D667 (with Emanuel Ax and Julius Levine)
 * Robert Schumann – Complete String Quartets, Op. 41, Piano Quintet in Eb Op. 44 (with Arthur Rubinstein)
 * Jean Sibelius – String Quartet in D minor Op. 56 Voces intimae
 * Bedřich Smetana – String Quartet in E minor ("From my Life")
 * Pyotr Ilyich Tchaikovsky – String Quartet No. 1 in D Op. 11, "Souvenir de Florence" Sextet Op. 70 (with Boris Kroyt and Mischa Schneider)
 * Giuseppe Verdi – String Quartet in E minor
 * Hugo Wolf – Italian Serenade

Awards

 * 2005:  The Ford Honors Award, University Musical Society of the University of Michigan.
 * 2004:  The Richard J. Bogomolny National Service Award, Chamber Music America.
 * 1992:  Award of Merit, Association of Performing Arts Presenters in New York City.
 * 1983:  Honorary Doctorate degrees by the State University of New York.
 * 1982:  New York Seal of Recognition.
 * 1976:  Honorary Doctorate degrees by the University of South Florida

Films

 * 1989: High Fidelity – The Guarneri String Quartet, directed and produced by Allan Miller.

Resources

 * David Blum (1986). The Art of Quartet Playing: The Guarneri Quartet in Conversation with David Blum, New York: Alfred A. Knopf Inc. ISBN 0-394-53985-0.
 * I. Fink & C. Merriell with the Guarneri String Quartet (1985). String Quartet Playing, New Jersey: Paganiniana Publications, Inc. ISBN 0-86622-007-0
 * Helen Drees Ruttencutter (1980). Quartet: a Profile of the Guarneri Quartet. New York. Lippincott & Crowell Publishers. ISBN 0-690-01944-0
 * Arnold Steinhardt (1998). Indivisible by Four: A String Quartet in Pursuit of Harmony, New York: Farrar, Straus and Giroux. ISBN 0-374-23670-4.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Guarneri Quartet


text:
Alas Purwo National Park

Alas Purwo National Park is situated on Blambangan Peninsula in the Banyuwangi Regency, at the southeastern tip of East Java province. The park is famous for its wild Banteng and surfing location at Grajagan Bay.

The park's name means first forest or ancient forest, following a Javanese legend that says the earth first emerged from the ocean here.

Geography
The park is located in Blambangan Peninsula at the southeastern tip of Java island, along the shore of the strait across Bali.

With an area of 434 km2, the park is made up of mangroves, savanna, lowland monsoon forests, and coral-fringed beaches. An internationally renowned surf break peels along the edge of the park at Plengkung on Grajagan Bay. Mount Linggamanis (322m) is also located in this national park.

Flora and fauna
The flora protected in this national park include Terminalia catappa, Calophyllum inophyllum, Sterculia foetida, Barringtonia asiatica, and Manilkara kauki.

It is home to some of Java’s endangered species, such as the banteng (Bos javanicus). In April 2004, there were only 57 bantengs found in the savanna of Sadengan, while the population in the previous year was estimated to be 80 to 100, but in August 2010, the scientists found 73 bantengs in the 80-hectare savanna area, a big increase in 6 years, although they faced threats of poaching and loss of habitat. Herds of bantengs usually come to Sadengan in the morning and afternoon in search of plants.

The biggest threat to the bantengs are humans. Poachers set traps outside the park during the dry season to snare bantengs wandering outside the park in search of water. The bantengs are slaughtered and the meat is sold.

Other threatened animal species protected in Alas Purwo include the dhole, Javan langur, green peafowl, red junglefowl, olive ridley, hawksbill turtle, and green turtle.

Surfing
Between the months of March and November, thousands of surfers from all over the world visit the park for its surf break. The destination is Plengkung Beach in Grajagan Bay, also known as G-Land, which is about half a day's travel from Bali.

The beach is considered one of the best surfing spots in Asia. With rideable waves up to 5 meters, it is considered a spot for experienced surfers only. The place is listed as Quicksilver World Tour Circuit.

title: Alas Purwo National Park


text:
Ile

Ile may refer to:

 * iLe, a Puerto Rican singer
 * Ile District (disambiguation), multiple places
 * Ilé-Ifẹ̀, an ancient Yoruba city in south-western Nigeria
 * Interlingue (ISO 639:ile), a planned language
 * Isoleucine, an amino acid abbreviated as Ile or I
 * Another name for Ilargi, the moon in Basque mythology
 * Historical spelling of Islay, Scottish island and girls' name
 * Another name for the Ili River in eastern Kazakhstan
 * Ile, a gender-neutral pronoun in Portuguese

title: Ile


text:
Talk:Vitali set

Lebesgue measure
Why must Lebesgue measure of Vitali set be larger than one? If we consider something like Vitali set for interval [0,0.5] its measure will be less than (or equal to) 0.5 Then this set will be also enough for interval [0,1], because we can simply add 0.5 (which is rational) for each real in [0,0.5]. Then we can add 1, 2, 3,... and we will have every real in it. Set from beginning is true Vitali set. We can do similarly for interval [0,0.25], [0,0.125], etc. so I consider that there are Vitali sets with arbitrary small measure, and possibly also 0. Then infinite sum argument won't be enough to prove non-measurability, because 0+0+0+0+...=0, which is finite — Preceding unsigned comment added by Wojowu (talk • contribs) 17:30, 6 January 2012 (UTC)

 * The Lebesgue measure of countably many different Vitali sets must be larger than one. But the Lebesque measure of each of those different Vitali sets must be identical because or translational invariance. Thats the problem. Neither zero nor something larger will work. YohanN7 (talk) 17:09, 6 September 2012 (UTC)

Minor Point
It would be nice not to try relying on things like physical intuition in the opening sentences explaining these ideas. Most particularly, I noticed some kind of phrase like "imagine metal rods with uniform density". I do not believe that type of phrase is appropriate to describe abstract general math results. — Preceding unsigned comment added by 71.201.95.139 (talk) 01:57, 8 December 2012 (UTC)

 * Agreed. Plus, I believe the section on measurable sets shouldn't even be there. It replicates (in a worse way) content from the Lebesgue Measure article, which is much more complete and contextualized. — Preceding unsigned comment added by Walwal20 (talk • contribs) 18:27, 10 April 2020 (UTC)

History?
The article doesn't mention any history about the concept. Was Lebesgue measure defined after vitali sets where found, or was lebesgue measure already defined and the vitaly sets where found? — Preceding unsigned comment added by 181.29.52.110 (talk) 02:50, 2 July 2015 (UTC)

The "construction"'section does not include an explicit construction
I'm not an expert in this area. I expected to see an explicit definition of a Vitali set in the "construction"section. Right now, there doesn't seem to be one. Grover cleveland (talk) 16:04, 26 October 2021 (UTC)
 * There is no "explicit definition" in the sense of a formula of first-order logic with one free variable, φ(x), such that provably in ZFC the set of all reals x such that φ(x) holds is a Vitali set.
 * (Just for completeness, there is a formula φ(x) such that ZFC does not refute that φ defines a Vitali set.)
 * But the word "construction" here is not intended to evoke constructive mathematics or anything like that. It's a construction in an informal sense — you do this, then you do that, then you do the other thing.  At various points you make arbitrary choices.  --Trovatore (talk) 17:47, 26 October 2021 (UTC)

Infinite parity function
The articles on the infinite parity function provides a construction that is more-or-less identical to the construction of the Vitali set. The difference is that it uses the dyadic rationals instead of the rationals in the construction. But, of course, the rationals and the dyadic rationals map to one-another (one-to-one, onto) using the Minkowski question mark function. I would add this to the article, except that this is extremely minor "original research" on my part (well, it seems plainly obvious to me, but hey...); that, and the fact that the construction in infinite parity function is muddled and unreferenced. So, at a minimum, that article should be fixed so that the construction there makes it clear that it is just the Vitali set.

To be more precise, the infinite parity function uses the Vitali-like construction to define an infinite parity function f (and there are uncountably many of these, since one is asked to choose a representative from each coset.) and then notes that $$f^{-1}(0)$$ is not a Borel set. Given the construction, it appears that $$f^{-1}(0)$$ contains countably many copies of the Vitali set, all of which are offset from each-other by some dyadic rational. Only half the dyadic rationals are used; the other half land in $$f^{-1}(1)$$. It seems to me that the Vitali set could also be defined in this way, thus showing that there are uncountably many different Vital sets. 67.198.37.16 (talk) 01:42, 28 November 2023 (UTC)

The Vitali-type construction also shows up in the "second proof" in the article on the Axiom of determinacy, except there, it takes the form of Cantor space (inifinite binary strings) mod finite binary strings. The Cantor space maps to the reals in the usual way, and the finite-length binary strings map to the dyadic rationals. So I've now seen the exact same construction in three different articles in 24 hours. Does it have a name? My personal neologism is "a Vitali-type construction", although it could be called "the Vitali-type construction", since it seems there is only one. 67.198.37.16 (talk) 06:16, 28 November 2023 (UTC)

New material on measure and AC
So added some interesting material about needing AC to prove that there's a non-measurable set, with a quibble that you might not need it if reality somehow manages to split the thin difference between ZFC and ZFC+"there exists an inaccessible cardinal". I made some minor tweaks to it.

But while the material is interesting, I'm not sure it belongs in exactly this article, at least in this form. If I remember correctly (and I don't have an immediate cite for this), you don't need the inaccessible to prove the consistency of ZF+"every set of reals has the property of Baire", which also refutes the existence of a Vitali set. So at least the stuff about the inaccessible cardinal seems to be more about measurable sets than about the Vitali set per se.

I wonder if it would fit better at non-measurable set? --Trovatore (talk) 06:01, 29 December 2023 (UTC)

 * The material should definitely be moved to non-measurable set where it properly belongs; this article could then just give a very short summary and refer people there. The result you mentioned is also very interesting and should be mentioned here, since it implies that "existence of non-measurable sets" and "existence of Vitali sets" are not exactly equivalent. Cheers, AxelBoldt (talk) 21:15, 31 December 2023 (UTC)

title: Talk:Vitali set


text:
Ribonuclease H

Ribonuclease H (abbreviated RNase H or RNH) is a family of non-sequence-specific endonuclease enzymes that catalyze the cleavage of RNA in an RNA/DNA substrate via a hydrolytic mechanism. Members of the RNase H family can be found in nearly all organisms, from bacteria to archaea to eukaryotes.

The family is divided into evolutionarily related groups with slightly different substrate preferences, broadly designated ribonuclease H1 and H2. The human genome encodes both H1 and H2. Human ribonuclease H2 is a heterotrimeric complex composed of three subunits, mutations in any of which are among the genetic causes of a rare disease known as Aicardi–Goutières syndrome. A third type, closely related to H2, is found only in a few prokaryotes, whereas H1 and H2 occur in all domains of life. Additionally, RNase H1-like retroviral ribonuclease H domains occur in multidomain reverse transcriptase proteins, which are encoded by retroviruses such as HIV and are required for viral replication.

In eukaryotes, ribonuclease H1 is involved in DNA replication of the mitochondrial genome. Both H1 and H2 are involved in genome maintenance tasks such as processing of R-loop structures.

Classification and nomenclature
Ribonuclease H is a family of endonuclease enzymes with a shared substrate specificity for the RNA strand of RNA-DNA duplexes. By definition, RNases H cleave RNA backbone phosphodiester bonds to leave a 3' hydroxyl and a 5' phosphate group. RNases H have been proposed as members of an evolutionarily related superfamily encompassing other nucleases and nucleic acid processing enzymes such as retroviral integrases, DNA transposases, Holliday junction resolvases, Piwi and Argonaute proteins, various exonucleases, and the spliceosomal protein Prp8.

RNases H can be broadly divided into two subtypes, H1 and H2, which for historical reasons are given Arabic numeral designations in eukaryotes and Roman numeral designations in prokaryotes. Thus the Escherichia coli RNase HI is a homolog of the Homo sapiens RNase H1. In E. coli and many other prokaryotes, the rnhA gene encodes HI and the rnhB gene encodes HII. A third related class, called HIII, occurs in a few bacteria and archaea; it is closely related to prokaryotic HII enzymes.

Structure
The structure of RNase H commonly consists of a 5-stranded β-sheet surrounded by a distribution of α-helices. All RNases H have an active site centered on a conserved sequence motif composed of aspartate and glutamate residues, often referred to as the DEDD motif. These residues interact with catalytically required magnesium ions.

RNases H2 are larger than H1 and usually have additional helices. The domain organization of the enzymes varies; some prokaryotic and most eukaryotic members of the H1 group have an additional small domain at the N-terminus known as the "hybrid binding domain", which facilitates binding to RNA:DNA hybrid duplexes and sometimes confers increased processivity. While all members of the H1 group and the prokaryotic members of the H2 group function as monomers, eukaryotic H2 enzymes are obligate heterotrimers. Prokaryotic HIII enzymes are members of the broader H2 group and share most structural features with H2, with the addition of an N-terminal TATA box binding domain. Retroviral RNase H domains occurring in multidomain reverse transcriptase proteins have structures closely resembling the H1 group.

RNases H1 have been extensively studied to explore the relationships between structure and enzymatic activity. They are also used, especially the E. coli homolog, as model systems to study protein folding. Within the H1 group, a relationship has been identified between higher substrate-binding affinity and the presence of structural elements consisting of a helix and flexible loop providing a larger and more basic substrate-binding surface. The C-helix has a scattered taxonomic distribution; it is present in the E. coli and human RNase H1 homologs and absent in the HIV RNase H domain, but examples of retroviral domains with C-helices do exist.

Function
Ribonuclease H enzymes cleave the phosphodiester bonds of RNA in a double-stranded RNA:DNA hybrid, leaving a 3' hydroxyl and a 5' phosphate group on either end of the cut site with a two-metal-ion catalysis mechanism, in which two divalent cations, such as Mg2+ and Mn2+, directly participate in the catalytic function. Depending on the differences in their amino acid sequences, these RNases H are classified into type 1 and type 2 RNases H. Type 1 RNases H have prokaryotic and eukaryotic RNases H1 and retroviral RNase H. Type 2 RNases H have prokaryotic and eukaryotic RNases H2 and bacterial RNase H3. These RNases H exist in a monomeric form, except for eukaryotic RNases H2, which exist in a heterotrimeric form. RNase H1 and H2 have distinct substrate preferences and distinct but overlapping functions in the cell. In prokaryotes and lower eukaryotes, neither enzyme is essential, whereas both are believed to be essential in higher eukaryotes. The combined activity of both H1 and H2 enzymes is associated with maintenance of genome stability due to the enzymes' degradation of the RNA component of R-loops.

Ribonuclease H1
Ribonuclease H1 enzymes require at least four ribonucleotide-containing base pairs in a substrate and cannot remove a single ribonucleotide from a strand that is otherwise composed of deoxyribonucleotides. For this reason, it is considered unlikely that RNase H1 enzymes are involved in the processing of RNA primers from Okazaki fragments during DNA replication. RNase H1 is not essential in unicellular organisms where it has been investigated; in E. coli, RNase H1 knockouts confer a temperature-sensitive phenotype, and in S. cerevisiae, they produce defects in stress response.

In many eukaryotes, including mammals, RNase H1 genes include a mitochondrial targeting sequence, leading to expression of isoforms with and without the MTS present. As a result, RNase H1 is localized to both mitochondria and the nucleus. In knockout mouse models, RNase H1-null mutants are lethal during embryogenesis due to defects in replicating mitochondrial DNA. The defects in mitochondrial DNA replication induced by loss of RNase H1 are likely due to defects in R-loop processing.

Ribonuclease H2
In prokaryotes, RNase H2 is enzymatically active as a monomeric protein. In eukaryotes, it is an obligate heterotrimer composed of a catalytic subunit A and structural subunits B and C. While the A subunit is closely homologous to the prokaryotic RNase H2, the B and C subunits have no apparent homologs in prokaryotes and are poorly conserved at the sequence level even among eukaryotes. The B subunit mediates protein-protein interactions between the H2 complex and PCNA, which localizes H2 to replication foci.

Both prokaryotic and eukaryotic H2 enzymes can cleave single ribonucleotides in a strand. however, they have slightly different cleavage patterns and substrate preferences: prokaryotic enzymes have lower processivity and hydrolyze successive ribonucleotides more efficiently than ribonucleotides with a 5' deoxyribonucleotide, while eukaryotic enzymes are more processive and hydrolyze both types of substrate with similar efficiency. The substrate specificity of RNase H2 gives it a role in ribonucleotide excision repair, removing misincorporated ribonucleotides from DNA, in addition to R-loop processing. Although both H1 and H2 are present in the mammalian cell nucleus, H2 is the dominant source of RNase H activity there and is important for maintaining genome stability.

Some prokaryotes possess an additional H2-type gene designated RNase HIII in the Roman-numeral nomenclature used for the prokaryotic genes. HIII proteins are more closely related to the H2 group by sequence identity and structural similarity, but have substrate preferences that more closely resemble H1. Unlike HI and HII, which are both widely distributed among prokaryotes, HIII is found in only a few organisms with a scattered taxonomic distribution; it is somewhat more common in archaea and is rarely or never found in the same prokaryotic genome as HI.

Mechanism

The active site of nearly all RNases H contains four negatively charged amino acid residues, known as the DEDD motif; often a histidine e.g. in HIV-1, human or E. coli is also present.

The charged residues bind two metal ions that are required for catalysis; under physiological conditions these are magnesium ions, but manganese also usually supports enzymatic activity, while calcium or high concentration of Mg2+ inhibits activity.

Based on experimental evidence and computer simulations the enzyme activates a water molecule bound to one of the metal ions with the conserved histidine. The transition state is associative in nature and forms an intermediate with protonated phosphate and deprotonated alkoxide leaving group. The leaving group is protonated via the glutamate which has an elevated pKa and is likely to be protonated. The mechanism is similar to RNase T and the RuvC subunit in the Cas9 enzyme which both also use a histidine and a two-metal ion mechanism.

The mechanism of the release of the cleaved product is still unresolved. Experimental evidence from time-resolved crystallography and similar nucleases points to a role of a third ion in the reaction recruited to the active site.

In human biology
The human genome contains four genes encoding RNase H:
 * RNASEH1, an example of the H1 (monomeric) subtype
 * RNASEH2A, the catalytic subunit of the trimeric H2 complex
 * RNASEH2B, a structural subunit of the trimeric H2 complex
 * RNASEH2C, a structural subunit of the trimeric H2 complex

In addition, genetic material of retroviral origin appears frequently in the genome, reflecting integration of the genomes of human endogenous retroviruses. Such integration events result in the presence of genes encoding retroviral reverse transcriptase, which includes an RNase H domain. An example is ERVK6. Long terminal repeat (LTR) and non-long terminal repeat (non-LTR) retrotransposons are also common in the genome and often include their own RNase H domains, with a complex evolutionary history.

Role in disease
In small studies, mutations in human RNase H1 have been associated with chronic progressive external ophthalmoplegia, a common feature of mitochondrial disease.

Mutations in any of the three RNase H2 subunits are well-established as causes of a rare genetic disorder known as Aicardi–Goutières syndrome (AGS), which manifests as neurological and dermatological symptoms at an early age. The symptoms of AGS closely resemble those of congenital viral infection and are associated with inappropriate upregulation of type I interferon. AGS can also be caused by mutations in other genes: TREX1, SAMHD1, ADAR, and MDA5/IFIH1, all of which are involved in nucleic acid processing. Characterization of mutational distribution in an AGS patient population found 5% of all AGS mutations in RNASEH2A, 36% in 2B, and 12% in 2C. Mutations in 2B have been associated with somewhat milder neurological impairment and with an absence of interferon-induced gene upregulation that can be detected in patients with other AGS-associated genotypes.

In viruses
Two groups of viruses use reverse transcription as part of their life cycles: retroviruses, which encode their genomes in single-stranded RNA and replicate through a double-stranded DNA intermediate; and dsDNA-RT viruses, which replicate their double-stranded DNA genomes through an RNA "pregenome" intermediate. Pathogenic examples include human immunodeficiency virus and hepatitis B virus, respectively. Both encode large multifunctional reverse transcriptase (RT) proteins containing RNase H domains.

Retroviral RT proteins from HIV-1 and murine leukemia virus are the best-studied members of the family. Retroviral RT is responsible for converting the virus' single-stranded RNA genome into double-stranded DNA. This process requires three steps: first, RNA-dependent DNA polymerase activity produces minus-strand DNA from the plus-strand RNA template, generating an RNA:DNA hybrid intermediate; second, the RNA strand is destroyed; and third, DNA-dependent DNA polymerase activity synthesizes plus-strand DNA, generating double-stranded DNA as the final product. The second step of this process is carried out by an RNase H domain located at the C-terminus of the RT protein.

RNase H performs three types of cleaving actions: non-specific degradation of the plus-strand RNA genome, specific removal of the minus-strand tRNA primer, and removal of the plus-strand purine-rich polypurine tract (PPT) primer. RNase H plays a role in the priming of the plus-strand, but not in the conventional method of synthesizing a new primer sequence. Rather RNase H creates a "primer" from the PPT that is resistant to RNase H cleavage. By removing all bases but the PPT, the PPT is used as a marker for the end of the U3 region of its long terminal repeat.

Because RNase H activity is required for viral proliferation, this domain has been considered a drug target for the development of antiretroviral drugs used in the treatment of HIV/AIDS and other conditions caused by retroviruses. Inhibitors of retroviral RNase H of several different chemotypes have been identified, many of which have a mechanism of action based on chelation of the active-site cations. Reverse-transcriptase inhibitors that specifically inhibit the polymerase function of RT are in widespread clinical use, but not inhibitors of the RNase H function; it is the only enzymatic function encoded by HIV that is not yet targeted by drugs in clinical use.

Evolution
RNases H are widely distributed and occur in all domains of life. The family belongs to a larger superfamily of nuclease enzymes and is considered to be evolutionarily ancient. In prokaryotic genomes, multiple RNase H genes are often present, but there is little correlation between occurrence of HI, HII, and HIII genes and overall phylogenetic relationships, suggesting that horizontal gene transfer may have played a role in establishing the distribution of these enzymes. RNase HI and HIII rarely or never appear in the same prokaryotic genome. When an organism's genome contains more than one RNase H gene, they sometimes have significant differences in activity level. These observations have been suggested to reflect an evolutionary pattern that minimizes functional redundancy among RNase H genes. RNase HIII, which is unique to prokaryotes, has a scattered taxonomic distribution and is found in both bacteria and archaea; it is believed to have diverged from HII fairly early.

The evolutionary trajectory of RNase H2 in eukaryotes, especially the mechanism by which eukaryotic homologs became obligate heterotrimers, is unclear; the B and C subunits have no apparent homologs in prokaryotes.

Applications
Because RNase H specifically degrades only the RNA in double-stranded RNA:DNA hybrids, it is commonly used as a laboratory reagent in molecular biology. Purified preparations of E. coli RNase HI and HII are commercially available. RNase HI is often used to destroy the RNA template after first-strand complementary DNA (cDNA) synthesis by reverse transcription. It can also be used to cleave specific RNA sequences in the presence of short complementary segments of DNA. Highly sensitive techniques such as surface plasmon resonance can be used for detection. RNase HII can be used to degrade the RNA primer component of an Okazaki fragment or to introduce single-stranded nicks at positions containing a ribonucleotide. A variant of hot start PCR, known as RNase H-dependent PCR or rhPCR, has been described using a thermostable RNase HII from the hyperthermophilic archaeon Pyrococcus abyssi. Of note, the ribonuclease inhibitor protein commonly used as a reagent is not effective at inhibiting the activity of either HI or HII.

History
Ribonucleases H were first discovered in the laboratory of Peter Hausen when researchers found RNA:DNA hybrid endonuclease activity in calf thymus in 1969 and gave it the name "ribonuclease H" to designate its hybrid specificity. RNase H activity was subsequently discovered in E. coli and in a sample of oncoviruses with RNA genomes during early studies of viral reverse transcription. It later became clear that calf thymus extract contained more than one protein with RNase H activity and that E. coli contained two RNase H genes. Originally, the enzyme now known as RNase H2 in eukaryotes was designated H1 and vice versa, but the names of the eukaryotic enzymes were switched to match those in E. coli to facilitate comparative analysis, yielding the modern nomenclature in which the prokaryotic enzymes are designated with Roman numerals and the eukaryotic enzymes with Arabic numerals. The prokaryotic RNase HIII, reported in 1999, was the last RNase H subtype to be identified.

Characterizing eukaryotic RNase H2 was historically a challenge, in part due to its low abundance. Careful efforts at purification of the enzyme suggested that, unlike the E. coli RNase H2, the eukaryotic enzyme had multiple subunits. The S. cerevisiae homolog of the E. coli protein (that is, the H2A subunit) was easily identifiable by bioinformatics when the yeast genome was sequenced, but the corresponding protein was found not to have enzymatic activity in isolation. Eventually, the yeast B and C subunits were isolated by co-purification and found to be required for enzymatic activity. However, the yeast B and C subunits have very low sequence identity to their homologs in other organisms, and the corresponding human proteins were conclusively identified only after mutations in all three were found to cause Aicardi–Goutières syndrome.

title: Ribonuclease H


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Ronquil

Ronquils (sometimes spelt ronchils) is a small family marine ray-finned fish, the Bathymasteridae. These fishes are found only in Arctic and North Pacific waters. This family contains just seven species in three genera. The larger species are important to commercial fisheries as food fish. Ronquils are most closely related to the eelpouts and prowfish in the suborder Zoarcoidei of the order Scorpaeniformes.

Taxonomy
The Bathymasteridae was first proposed as a family in 1883 by the American ichthyologists David Starr Jordan and Charles Henry Gilbert. The 5th edition of Fishes of the World classifies this family within the suborder Zoarcoidei, within the order Scorpaeniformes. Other authorities classify this family in the infraorder Zoarcales within the suborder Cottoidei of the Perciformes because removing the Scorpaeniformes from the Perciformes renders that taxon non monophyletic. The monophyly of the Zoarcoidei has still not been fully ascertained but it is generally accepted that the most basal family is Bathymasteridae.

Etymology
The name ronquil is said to be an anglicization from the Spanish ronco, ronquillo being a diminutive, and which means “one who grunts”. The family name Bathymasteridae is derived from the type genus Bathymaster and this can be translated from the Greek to mean "deep searcher".

Genera
The ronquil family is divided into three genera as follows:

Characteristics
Ronquils have elongate with long dorsal and anal fins which are even in height along all of their length. These fins are separated from the large, truncate to round caudal fin by a clear caudal peduncle. There are between 43 and 49 branched and unbranched rays in the dorsal fin while the anal fin contains between 31 and 36 rays. These ray counts include between 1 and 6 weak, pliant to the front of the dorsal fin and 1 or 2 similar spines in the front of the anal fin. The pectoral fins are large and rounded while the pelvic fins are located on the thorax, and have a single spine and 5 soft rays. There is a single pair of nostrils. The scales vary from weakly ctenoid, nearly smooth, to strongly ctenoid. There are sensory pores on the upper head of head and on the cheeks and these are obvious. The lateral line is clearly visible and runs on the upper body, straight to the rear of the dorsal fin, and has between 75 and 105 scales. The roof of the mouth has palatine and vomerine teeth. The bill membrane is separate from the isthmus, in most cases. There is no swim bladder. These fishes may be olive brown to dull red, bluish black, or purplish in their overall colour, they can be marked with bright green, blue, yellow, red, orange, and white bars, spots or other markings. The colour and patterns often vary between populations or be an expression of sexual dimorphism. Ronquins vary in size from a  total length of 20 cm in Ronquilus jordani to more over 38 cm for Bathymaster signatus.

Distribution, habitat and behaviour
Ronqulis inhabit cold waters in the North Pacific where they have a wide range from Baja California to the Sea of Japan, ronquils are benthic animals, spending most of their time on or near the bottom. These fishes are typically found in shallow coastal waters down to depths of around 200 m, however, Bathymaster signatus has been taken from depths in excess of 300 m in the Bering Sea and Aleutian Islands.

Ronquils feed primarily on small benthic crustaceans and mollusks, and the stomachs of some specimens sampled contained only nudibranch]s. Little is known about predators of ronqulis but it is presumed that most larger carnivores that occur in the same areas as them, especially predatory fishes, will prey on them. Although considered fairly common, ronquils are rarely observed; this is likely owing to their secretive nature.

Few specifics are recorded regarding ronquil spawning, but the males are known to guard the brood. The males have been known to cannibalize some of the eggs they are guarding.

title: Ronquil


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DNA polymerase I

DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. Discovered by Arthur Kornberg in 1956, it was the first known DNA polymerase (and the first known of any kind of polymerase). It was initially characterized in E. coli and is ubiquitous in prokaryotes. In E. coli and many other bacteria, the gene that encodes Pol I is known as polA. The E. coli Pol I enzyme is composed of 928 amino acids, and is an example of a processive enzyme — it can sequentially catalyze multiple polymerisation steps without releasing the single-stranded template. The physiological function of Pol I is mainly to support repair of damaged DNA, but it also contributes to connecting Okazaki fragments by deleting RNA primers and replacing the ribonucleotides with DNA.

Discovery
In 1956, Arthur Kornberg and colleagues discovered Pol I by using Escherichia coli (E. coli) extracts to develop a DNA synthesis assay. The scientists added 14C-labeled thymidine so that a radioactive polymer of DNA, not RNA, could be retrieved. To initiate the purification of DNA polymerase, the researchers added streptomycin sulfate to the E. coli extract. This separated the extract into a nucleic acid-free supernatant (S-fraction) and nucleic acid-containing precipitate (P-fraction). The P-fraction also contained Pol I and heat-stable factors essential for the DNA synthesis reactions. These factors were identified as nucleoside triphosphates, the building blocks of nucleic acids. The S-fraction contained multiple deoxynucleoside kinases. In 1959, the Nobel Prize in Physiology or Medicine was awarded to Arthur Kornberg and Severo Ochoa "for their discovery of the mechanisms involved in the biological synthesis of Ribonucleic acid and Deoxyribonucleic Acid."

General structure
Pol I mainly functions in the repair of damaged DNA. Structurally, Pol I is a member of the alpha/beta protein superfamily, which encompasses proteins in which α-helices and β-strands occur in irregular sequences. E. coli DNA Pol I consists of multiple domains with three distinct enzymatic activities. Three domains, often referred to as thumb, finger and palm domain work together to sustain DNA polymerase activity. A fourth domain next to the palm domain contains an exonuclease active site that removes incorrectly incorporated nucleotides in a 3' to 5' direction in a process known as proofreading. A fifth domain contains another exonuclease active site that removes DNA or RNA in a 5' to 3' direction and is essential for RNA primer removal during DNA replication or DNA during DNA repair processes.

E. coli bacteria produces 5 different DNA polymerases: DNA Pol I, DNA Pol II, DNA Pol III, DNA Pol IV, and DNA Pol V.

Structural and functional similarity to other polymerases
In DNA replication, the leading DNA strand is continuously extended in the direction of replication fork movement, whereas the DNA lagging strand runs discontinuously in the opposite direction as Okazaki fragments. DNA polymerases also cannot initiate DNA chains so they must be initiated by short RNA or DNA segments known as primers. In order for DNA polymerization to take place, two requirements must be met. First of all, all DNA polymerases must have both a template strand and a primer strand. Unlike RNA, DNA polymerases cannot synthesize DNA from a template strand. Synthesis must be initiated by a short RNA segment, known as RNA primer, synthesized by Primase in the 5' to 3' direction. DNA synthesis then occurs by the addition of a dNTP to the 3' hydroxyl group at the end of the preexisting DNA strand or RNA primer. Secondly, DNA polymerases can only add new nucleotides to the preexisting strand through hydrogen bonding. Since all DNA polymerases have a similar structure, they all share a two-metal ion-catalyzed polymerase mechanism. One of the metal ions activates the primer 3' hydroxyl group, which then attacks the primary 5' phosphate of the dNTP. The second metal ion will stabilize the leaving oxygen's negative charge, and subsequently chelates the two exiting phosphate groups.

The X-ray crystal structures of polymerase domains of DNA polymerases are described in analogy to human right hands. All DNA polymerases contain three domains. The first domain, which is known as the "fingers domain", interacts with the dNTP and the paired template base. The "fingers domain" also interacts with the template to position it correctly at the active site. Known as the "palm domain", the second domain catalyses the reaction of the transfer of the phosphoryl group. Lastly, the third domain, which is known as the "thumb domain", interacts with double stranded DNA. The exonuclease domain contains its own catalytic site and removes mispaired bases. Among the seven different DNA polymerase families, the "palm domain" is conserved in five of these families. The "finger domain" and "thumb domain" are not consistent in each family due to varying secondary structure elements from different sequences.

Function
Pol I possesses four enzymatic activities:

In order to determine whether Pol I was primarily used for DNA replication or in the repair of DNA damage, an experiment was conducted with a deficient Pol I mutant strain of E. coli. The mutant strain that lacked Pol I was isolated and treated with a mutagen. The mutant strain developed bacterial colonies that continued to grow normally and that also lacked Pol I. This confirmed that Pol I was not required for DNA replication. However, the mutant strain also displayed characteristics which involved extreme sensitivity to certain factors that damaged DNA, like UV light. Thus, this reaffirmed that Pol I was more likely to be involved in repairing DNA damage rather than DNA replication.
 * 1) A 5'→3' (forward) DNA-dependent DNA polymerase activity, requiring a 3' primer site and a template strand
 * 2) A 3'→5' (reverse) exonuclease activity that mediates proofreading
 * 3) A 5'→3' (forward) exonuclease activity mediating nick translation during DNA repair.
 * 4) A 5'→3' (forward) RNA-dependent DNA polymerase activity. Pol I operates on RNA templates with considerably lower efficiency (0.1–0.4%) than it does DNA templates, and this activity is probably of only limited biological significance.

Mechanism
In the replication process, RNase H removes the RNA primer (created by primase) from the lagging strand and then polymerase I fills in the necessary nucleotides between the Okazaki fragments (see DNA replication) in a 5'→3' direction, proofreading for mistakes as it goes. It is a template-dependent enzyme—it only adds nucleotides that correctly base pair with an existing DNA strand acting as a template. It is crucial that these nucleotides are in the proper orientation and geometry to base pair with the DNA template strand so that DNA ligase can join the various fragments together into a continuous strand of DNA. Studies of polymerase I have confirmed that different dNTPs can bind to the same active site on polymerase I. Polymerase I is able to actively discriminate between the different dNTPs only after it undergoes a conformational change. Once this change has occurred, Pol I checks for proper geometry and proper alignment of the base pair, formed between bound dNTP and a matching base on the template strand. The correct geometry of A=T and G≡C base pairs are the only ones that can fit in the active site. However, it is important to know that one in every 104 to 105 nucleotides is added incorrectly. Nevertheless, Pol I can fix this error in DNA replication using its selective method of active discrimination.

Despite its early characterization, it quickly became apparent that polymerase I was not the enzyme responsible for most DNA synthesis—DNA replication in E. coli proceeds at approximately 1,000 nucleotides/second, while the rate of base pair synthesis by polymerase I averages only between 10 and 20 nucleotides/second. Moreover, its cellular abundance of approximately 400 molecules per cell did not correlate with the fact that there are typically only two replication forks in E. coli. Additionally, it is insufficiently processive to copy an entire genome, as it falls off after incorporating only 25–50 nucleotides. Its role in replication was proven when, in 1969, John Cairns isolated a viable polymerase I mutant that lacked the polymerase activity. Cairns' lab assistant, Paula De Lucia, created thousands of cell free extracts from E. coli colonies and assayed them for DNA-polymerase activity. The 3,478th clone contained the polA mutant, which was named by Cairns to credit "Paula" [De Lucia]. It was not until the discovery of DNA polymerase III that the main replicative DNA polymerase was finally identified.

Research applications
DNA polymerase I obtained from E. coli is used extensively for molecular biology research. However, the 5'→3' exonuclease activity makes it unsuitable for many applications. This undesirable enzymatic activity can be simply removed from the holoenzyme to leave a useful molecule called the Klenow fragment, widely used in molecular biology. In fact, the Klenow fragment was used during the first protocols of polymerase chain reaction (PCR) amplification until Thermus aquaticus, the source of a heat-tolerant Taq Polymerase I, was discovered in 1976. Exposure of DNA polymerase I to the protease subtilisin cleaves the molecule into a smaller fragment, which retains only the DNA polymerase and proofreading activities.

title: DNA polymerase I