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Reverse transcriptase

A reverse transcriptase is an enzyme used to generate complementary DNA from an RNA template, a process termed reverse transcription. Reverse transcriptases are used by retroviruses to replicate their genomes, by retrotransposon mobile genetic elements to proliferate within the host genome, by eukaryotic cells to extend the telomeres at the ends of their linear chromosomes, by some non-retroviruses such as the hepatitis B virus, a member of the Hepadnaviridae, which are dsDNA-RT viruses. Retroviral RT has three sequential biochemical activities: RNA-dependent DNA polymerase activity, ribonuclease H, DNA-dependent DNA polymerase activity. Collectively, these activities enable the enzyme to convert single-stranded RNA into double-stranded cDNA. In retroviruses and retrotransposons, this cDNA can integrate into the host genome, from which new RNA copies can be made via host-cell transcription; the same sequence of reactions is used in the laboratory to convert RNA to DNA for use in molecular cloning, RNA sequencing, polymerase chain reaction, or genome analysis.

Reverse transcriptases were discovered by Howard Temin at the University of Wisconsin–Madison in Rous sarcoma virions and independently isolated by David Baltimore in 1970 at MIT from two RNA tumour viruses: murine leukemia virus and again Rous sarcoma virus. For their achievements, they shared the 1975 Nobel Prize in Medicine. Well-studied reverse transcriptases include: HIV-1 reverse transcriptase from human immunodeficiency virus type 1 has two subunits, which have respective molecular weights of 66 and 51 kDa. M-MLV reverse transcriptase from the Moloney murine leukemia virus is a single 75 kDa monomer. AMV reverse transcriptase from the avian myeloblastosis virus has two subunits, a 63 kDa subunit and a 95 kDa subunit. Telomerase reverse transcriptase; the enzymes are encoded and used by viruses that use reverse transcription as a step in the process of replication. Reverse-transcribing RNA viruses, such as retroviruses, use the enzyme to reverse-transcribe their RNA genomes into DNA, integrated into the host genome and replicated along with it.

Reverse-transcribing DNA viruses, such as the hepadnaviruses, can allow RNA to serve as a template in assembling and making DNA strands. HIV infects humans with the use of this enzyme. Without reverse transcriptase, the viral genome would not be able to incorporate into the host cell, resulting in failure to replicate. Reverse transcriptase creates double-stranded DNA from an RNA template. In virus species with reverse transcriptase lacking DNA-dependent DNA polymerase activity, creation of double-stranded DNA can be done by host-encoded DNA polymerase δ, mistaking the viral DNA-RNA for a primer and synthesizing a double-stranded DNA by similar mechanism as in primer removal, where the newly synthesized DNA displaces the original RNA template; the process of reverse transcription is error-prone, it is during this step that mutations may occur. Such mutations may cause drug resistance. Retroviruses referred to as class VI ssRNA-RT viruses, are RNA reverse-transcribing viruses with a DNA intermediate.

Their genomes consist of two molecules of positive-sense single-stranded RNA with a 5' cap and 3' polyadenylated tail. Examples of retroviruses include the human immunodeficiency virus and the human T-lymphotropic virus. Creation of double-stranded DNA occurs in the cytosol as a series of these steps: Lysyl tRNA acts as a primer and hybridizes to a complementary part of the virus RNA genome called the primer binding site or PBS. Reverse transcriptase adds DNA nucleotides onto the 3' end of the primer, synthesizing DNA complementary to the U5 and R region of the viral RNA. A domain on the reverse transcriptase enzyme called RNAse H degrades the U5 and R regions on the 5’ end of the RNA; the tRNA primer "jumps" to the 3’ end of the viral genome, the newly synthesised DNA strands hybridizes to the complementary R region on the RNA. The complementary DNA added in is further extended; the majority of viral RNA is degraded by RNAse H. Synthesis of the second DNA strand begins; the tRNA primer leaves and a "jump" happens.

The PBS from the second strand hybridizes with the complementary PBS on the first strand. Both strands are extended to form a complete double-stranded DNA copy of the original viral RNA genome, which can be incorporated into the host's genome by the enzyme integrase. Creation of double-stranded DNA involves strand transfer, in which there is a translocation of short DNA product from initial RNA-dependent DNA synthesis to acceptor template regions at the other end of the genome, which are reached and processed by the reverse transcriptase for its DNA-dependent DNA activity. Retroviral RNA is arranged in 5’ terminus to 3’ terminus; the site where the primer is annealed to viral RNA is called the primer-binding site. The RNA 5’end to the PBS site is called U5, the RNA 3’ end to the PBS is called the leader; the tRNA primer is unwound between 14 and 22 nucleotides and forms a base-paired duplex with the viral RNA at PBS. The fact that the PBS is located near the 5’ terminus of viral RNA is unusual because reverse transcriptase synthesize DNA from 3’ end of the primer in the 5’ to 3’ direction.

Therefore, the primer and reverse transcriptase must be relocated to 3’ end of viral RNA. In order to accomplish this reposition, multiple steps and various enzymes including DNA polymerase, ribonuclease H and polynucleotide

1950 Michigan Wolverines football team

The 1950 Michigan Wolverines football team was an American football team that represented the University of Michigan in the 1950 Big Nine Conference football season. Coached by Bennie Oosterbaan, the Wolverines won the Big Ten Conference championship with a record of 6–3–1 and defeated the California Bears in the 1951 Rose Bowl, 14–6; the team had two All-Big 10 backs in Don Dufek and Chuck Ortmann and All-American tackle R. Allen "Brick" Wahl. Despite losing three times and tying once, Michigan was ranked #9 in the AP Poll and #6 in the UPI Poll at season's end; the Wolverines played a regular season game at Yankee Stadium against Army on October 14, 1950, losing 27–6. Michigan, ranked No. 3 in the country, opened the 1950 season playing against Michigan State College in Ann Arbor. Though favored by two touchdowns, the Wolverines were upset by the Spartans 14-7; the defeat was Michigan's first loss in the opening game of a season since 1937. Michigan played most of the game without Chuck Ortmann.

Ortmann was injured while being tackled on a 35-yard kickoff return in the first quarter. On the next play, Ortmann dropped back to pass but fell to the ground and was unable to return to the game. Michigan State took a 7-0 lead in the first quarter on a touchdown run by Sonny Grandelius. Michigan tied the score in the third quarter on a touchdown pass from Don Peterson to Fred Pickard. Michigan's touchdown was set up when Frank Howell intercepted a Michigan State pass and returned it 32 yards to the Michigan State 20-yard line. In the fourth quarter, Michigan State returned a punt to the Michigan 19-yard line and scored on a run by Michigan State fullback Leroy Crane. Michigan drove to the Michigan State 10-yard line in the fourth quarter, but the drive ended when quarterback Bill Putich threw an interception. Michigan rebounded in the second week of the season with a 27-7 win over Dartmouth at Michigan Stadium. Dartmouth scored first with a touchdown pass from Johnny Clayton to John McDonald.

Leo Koceski scored Michigan's first touchdown on 36-yard end run in the first quarter. Sophomore Lowell Perry caught a 21-yard touchdown pass from Bill Putich near the end of the first half to give Michigan a 13-7 lead at halftime. Perry had three interceptions on defense. Michigan scored two touchdowns in the third quarter, one on a long pass from Don Peterson to Harry Allis; the final touchdown came. Fullback Ralph Staffon ran for the touchdown. In the third game of the 1950 season, Michigan faced an Army team, ranked No. 1 in the AP and Coaches' Polls at Yankee Stadium in New York. The two teams played to a 6-6 tie at halftime, but Army shut out the Wolverines 21-0 in the second half for a final score of 27-6; the game marked the 23rd consecutive victory by Army. Chuck Ortmann threw for 118 yards, Don Dufek gained 66 yards on the ground and scored Michigan's one touchdown. In the fourth game of the season, Michigan played Wisconsin in Ann Arbor. Michigan came into the game unranked with a 1-2 record, while Wisconsin was undefeated and ranked No. 15 in the Coaches' Poll.

Chuck Ortmann ran 16 yards for a touchdown in the first quarter and threw a 29-yard touchdown pass to Bill Putich in the second quarter to give Michigan a 14-0 lead at halftime. Don Dufek ran one yard for a touchdown in the third quarter. Dufek scored Michigan's final touchdown after intercepting a pass thrown by Wisconsin quarterback Bob Petruska. In the fourth quarter, Wisconsin closed the gap, scoring two touchdowns while playing against Michigan's reserves. In its fifth game, Michigan traveled to Minneapolis to play Minnesota. After a scoreless first half, Michigan drove down the field culminating in a two-yard run by Don Dufek. Minnesota tied the game with a touchdown in the final two minutes to tie the game at 7-7. Dufek rushed for 63 yards, but the Minnesota team held Michigan to a total of only 46 yards rushing as Chuck Ortmann was held to -38 rushing yards. With the tie game, Michigan retained possession of the Little Brown Jug. In the sixth game of the year, Michigan played Illinois in a swirling snowstorm at Michigan Stadium.

The cold temperature and slippery playing surface kept the offensive units of both teams in check. Chuck Ortmann went 0 for 11 passing, the Michigan offense was limited to 119 yards of total offense—all gained on the ground; because of the inclement weather, the game was reduced to a punting duel between Don Laz of Illinois and Tony Momsen of Michigan. There were 14 by Michigan and 11 by Illinois. Near the end of the first half, Illinois put together the only sustained drive of the game. Starting at its own 20-yard line, Illinois drove 80 yards for the game's only touchdown, converting on a ten-yard pass from Fred Major to Tony Klimek. In the seventh game of the season, Michigan defeated Indiana 20-7 at Michigan Stadium. Michigan scored on the third play of the game when Harry Allis intercepted a pass thrown by Lou D'Achille and returned it 33 yards for a touchdown; the Wolverines' offense received help from an unexpected source in Wes Bradford, a 155-pound, fifth-string scatback from Troy, Ohio.

Bradford rushed for 105 yards on 15 carries and scored his first career touchdown on a 41-yard run in the second quarter. Don Dufek scored Michigan's final touchdown on a 54-yard run on the first running play of the second half. In the eighth game of the season, Michigan had its biggest offensive output of the year, defeating Northwestern 34-23 at Michigan Stadium. Having averaged only 13 points a game in the first seven-game, Michigan scored in touchdowns in all four quarters against the Wildcats. Michigan's offense was led by a running game that gained 291 net yards, including 110 yards from Don Dufek and 76 yar

The Bard of Blood

The Bard of Blood is a 2015 Indian fictional espionage thriller novel written by debutant author, Bilal Siddiqi. He wrote the novel at the age of 20 during his college days in Mumbai, it was published by Penguin books. Kabir Anand, is a former Research and Analysis Wing agent and now a professor of Shakespeare in Mumbai, he was forced to leave RAW after a disastrous mission in Balochistan. He is called by the agency to return after Sadiq Sheikh, his ex-boss is killed. Meanwhile, Mullah Omar and the ISI are after him. Siddiqi said that he got a "sudden growing interest in the covert world of espionage" at the age of 17 and "the entire talk of jihad and Islamic extremism that plagued every newspaper." He started writing it at the age of 19 and met Chiki Sarkar, the Chief Editor of Penguin Books, through Hussain Zaidi whom he had been assisting for a few years. Zaidi had recommended Siddiqui's name to Sarkar, she read the half manuscript and decided to publish it. It took him "roughly a year". In November 2017, it was announced that a Netflix original eight-episode series will be made based on the novel, co-produced by Shah Rukh Khan.

The screenplay is written by Siddiqui. The cast includes Emraan Hashmi, Vineet Kumar Singh, Amyra Dastur, Shashank Arora, Kirti Kulhari, Sobhita Dhulipala, Jaideep Ahlawat, Suhail Nayyar and Ajay Mahendru; the Bard of Blood at Penguin Books