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Mechanism in vivo[edit]
Further information: DNA replication § The replication fork

The lagging strand of DNA is that strand of the DNA double helix that is orientated in a 5′ to 3′ manner. Therefore, its complement must be synthesized in a 3′→5′ manner. Because DNA polymerase III cannot synthesize in the 3′→5′ (of the DNA helix)[1] direction, the lagging strand is synthesized in short segments known as Okazaki fragments. Along the lagging strand's template, primase builds RNA primers in short bursts. DNA polymerases are then able to use the free 3′-OH groups on the RNA primers to synthesize DNA in the 5′→3′ direction.

The RNA fragments are then removed by DNA polymerase I for prokaryotes or DNA polymerase δ for eukaryotes (different mechanisms are used in eukaryotes and prokaryotes) and new deoxyribonucleotides are added to fill the gaps where the RNA was present. DNA ligase then joins the deoxyribonucleotides together, completing the synthesis of the lagging strand.

Primer removal[edit]

In eukaryotic primer removal, DNA polymerase δ extends the Okazaki fragment in 5′ to 3′ direction, and when it encounters the RNA primer from the previous Okazaki fragment, it displaces the 5′ end of the primer into a single-stranded RNA flap, which is removed by nuclease cleavage. Cleavage of the RNA flaps involves either flap structure-specific endonuclease 1 (FEN1) cleavage of short flaps, or coating of long flaps by the single-stranded DNA binding protein replication protein A (RPA) and sequential cleavage by Dna2 nuclease and FEN1.[2]

This mechanism is a potential explanation of how the HIV virus can transform its genome into double-stranded DNA from the RNA-DNA formed after reverse transcription of its RNA. However, the HIV-encoded reverse transcriptase has its own ribonuclease activity that degrades the viral RNA during the synthesis of cDNA, as well as DNA-dependent DNA polymerase activity that copies the sense cDNA strand into antisense DNA to form a double-stranded DNA intermediate.[3]

In addition to full-screen video, FLIP logs a transcript of the video, making it easy to find using FLIP’s built-in search engine.

Christopher Savoie, founder and chief executive of a start-up called Zapata, offered jobs this year to three scientists who specialize in an increasingly important technology called quantum computing. They accepted.

Several months later, the Cambridge, Mass., company was still waiting for the State Department to approve visas for the specialists. All three are foreigners, born in Europe and Asia.

Christopher Savoie, founder and chief executive of a start-up called Zapata, offered jobs this year to three scientists who specialize in an increasingly important technology called quantum computing. They accepted.

Several months later, the Cambridge, Mass., company was still waiting for the State Department to approve visas for the specialists. All three are foreigners, born in Europe and Asia.

A very important video for students, parents and teachers to understand how Indian education system needs to be improved. This video brings some serious concerns of a student's mindset and future. This case study in hindi is presented by Himeesh Madaan, who is a performance coach and motivational speaker. This video will also add to student motivation and help them in achieving more happiness and content in life. We hope this video on education system in India will bring a positive change in country. Curated by: Team Himeesh

The group project is a much-dreaded component of undergraduate courses, doubly so if students are expected to create their own project from scratch. However, instructors consistently return to the independent group project as an exercise that, if done properly, stimulates student inquiry and cooperation. In this post, I reflect on my experiences facilitating student-led group projects in a biology course and relate these experiences to the commonalities of independent group work across disciplines. I outline four common issues related to independent group projects, then provide the rationale for managing each issue to maximize learning outcomes.