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DNA Replication

DNA Replication. Replication Facts. DNA has to be copied before a cell divides DNA is copied during mitosis and meiosis New cells will need identical DNA strands. 3’. Parental DNA Molecule. 5’. Replication Fork. 3’. 5’. DNA Replication.

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DNA Replication

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  1. DNA Replication

  2. Replication Facts • DNA has to be copied before a cell divides • DNA is copied during mitosis and meiosis • New cells will need identical DNA strands

  3. 3’ Parental DNA Molecule 5’ Replication Fork 3’ 5’ DNA Replication • Two strands of the DNA molecule open forming replication forks • New strands grow at the forks

  4. Bubbles Bubbles DNA Replication • As the 2 DNA strands open at the origin, replication bubbles form • Prokaryotes (bacteria) have a single bubble • Eukaryotic chromosomes have MANY bubbles

  5. DNA Replication • Helicase “unzips” and separates the 2 DNA strands by breaking the weak hydrogen bonds • Binding proteinsattach and keep the 2 DNA strands separated

  6. DNA Replication • Before new DNA strands can form, there must be RNA primers present to start the addition of new nucleotides • DNA polymerase can then add the new nucleotides

  7. 5 O 3 3 O P P 5 5 C O G 1 3 2 4 4 2 1 3 5 O P P T A 3 5 O O 5 P P 3 Remember the Strands are Antiparallel

  8. 5’ 3’ 5’ RNA Primer DNA Polymerase Nucleotides Synthesis of the New DNA Strands • The leading strandis synthesized as a single strand from the point of origin toward the opening replication fork

  9. Proofreading New DNA • DNA polymerase initially makes about 1 in 10,000 errors • Other enzymes proofread and correct these mistakes • The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors

  10. DNA Template Parental DNA New DNA Semiconservative Model of Replication • The two strands of the parental molecule separate, and each acts as a template for a new strand • New DNA has 1 ORIGINAL and 1 NEW strand of DNA

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