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Understanding DNA Structure and Replication in Cells

This overview explores the fundamental concepts of DNA, focusing on its structure and the intricate process of DNA replication. We delve into the stages of the cell cycle, the role of enzymes like helicase and DNA polymerase, and the importance of precision in copying genetic material. With each step, we outline how helicase unwinds DNA, polymerase synthesizes new strands, and ligase seals any gaps. Prepare to refresh your knowledge and visualize the critical processes that underlie biological inheritance and cellular function.

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Understanding DNA Structure and Replication in Cells

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  1. Where is DNA found within the cell? Quick Question #1 Lets refresh our knowledge of DNA structure http://www.youtube.com/watch?v=ZGHkHMoyC5I

  2. What occurs during the cell cycle? Quick Question #2

  3. DNA REPLICATION • Copying of DNA • An extremely precise process • Copies in sections, not from one end to the other • Basis of biological inheritance

  4. Replication Process • Three step process • Each step controlled by one of three enzymes (enzymes always end in –aseso look out for them in these notes) • Directional: always starts at a 5’ end of DNA strands and builds onto the 3’ end: • Copies both strands simultaneously starting at the replication fork.

  5. What do you think needs to happen in order for replication to start Quick Question #3

  6. Replication: Step One Facilitated by: Helicase • Helicase enzyme unwinds and unzips DNA strands • breaks hydrogen bonds QQ#4 What do you think will needs to happen for the DNA to “unzip”?

  7. A G G C T C C G DNAPolymerase Replication: Step Two Facilitated by: DNA Polymerase • DNA Polymerase enzyme: • reads a base on one side • Then adds complementary (matching) base to the other • e.g.

  8. Step 2 Continued • Both sides replicated to create two new strands of DNA each with: • -One original and One new strand

  9. Step 2 Continued • Strands are replicated from 5’ to 3’ and go in opposite directions • One side is replicated in a continuous piece: • -Leading Strand • Other side is replicated in short pieces: • -Lagging Strand • Okazaki Fragments

  10. Replication: Step Three Facilitated by: Ligase • Ligase enzyme • Glues (ties) DNA all together • Very important for Okazaki Fragments-closes any gaps between them

  11. Draw a visual that helps YOU remember the 3 steps of replication Quick Question #5

  12. Overall Process of Replication http://www.youtube.com/watch?v=teV62zrm2P0

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