dna replication n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
DNA Replication PowerPoint Presentation
Download Presentation
DNA Replication

Loading in 2 Seconds...

play fullscreen
1 / 13

DNA Replication - PowerPoint PPT Presentation


  • 74 Views
  • Uploaded on

DNA Replication. Review. Why is the process of DNA called a semiconservative process? Let’s review DNA structure: List all characteristics you can recall about DNA molecule. A closer look. Today we will learn about some incredible stuff happening in your body right now! (p.313).

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'DNA Replication' - yul


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
review
Review
  • Why is the process of DNA called a semiconservative process?
  • Let’s review DNA structure:
    • List all characteristics you can recall about DNA molecule
a closer look
A closer look
  • Today we will learn about some incredible stuff happening in your body right now! (p.313)
getting started
Getting Started
  • DNA replication begins @ particular sites called origins of replication
    • Proteins attach and begin copying DNA strand
      • Forms replication bubble  could be multiple in single DNA helix = speeds up replication process
      • At each end of bubble = replication forks: the y=shaped region where parts of parental DNA being unwound

DRAW pic. on pg. 313

proteins involved in unwinding
Proteins involved in unwinding
  • Helicase: untwists/unzips DNA at forks =opens up template strands
  • Single –strand binding proteins: bind to unwound parental strands, keeping them from re-pairing
  • Topoisomerase: helps relieve strain on unwound DNA while unwinding is occurring  so DNA does not break permanently
replication initiation
Replication Initiation
  • Enzymes that add nucleotides need help to start… can’t initiate process on their own
    • initial nucleotide chain is added = a short RNA chain called a primer created by enzyme called primase

-usually 5-10 nucleotides long

*new DNA strand will start from 3’ end of primer

adding bases
Adding Bases
  • Main protein involved = DNA polymerase

 Specifically DNA polymerase I (DNA pol I) and DNA polymerase III (DNA pol III)

  • After primer added, polymerase will begin adding nucleoside triphosphates (dATP) to the strand
    • Similar to ATP except sugar: ATP = ribose, dATP = deoxyribose

 When added to template, 2 phosphates break off (b/c unstable) = exergonic reaction that drives polymerization

antiparallel elongation
Antiparallel Elongation
  • DNA strands/replication has directionality (like 1 way street)  compliment strands are antiparallel

How does the antiparallel arrangement of the double helix affect replication?

(HINT: think back to the rule of the primer)

answer
Answer:
  • DNA pol can only add bases to 3’ end of primer .. So a new DNA strand can ONLY elongate from 5’-3’ direction

Let’s take a closer look at replication forks of the bubble to see how this works!

antiparallel elongation1
Antiparallel Elongation
  • 1st strand, DNA pol III can synthesize complimentary strand continuously as DNA unwinds from 5’ – 3’ direction

= LEADING STRAND

    • Only 1 primer needed
  • 2nd strand, DNA pol III must work in opposite direction (away from replication fork) to continue replication in 5’ – 3’ direction

= LAGGING STRAND

 Synthesized discontinuously in segments called Okazaki fragments

what do we do with the primer
What do we do with the primer?
  • When segment replication is complete, primer must be removed
      • DNA pol I comes in and removes RNA primer and fills hole with DNA nucleotides
      • An enzyme called DNA ligase comes in and patches two segments of lagging strand together

Let’s see it in action!

review1
Review:
  • For the following enzymes/proteins, list their roles in DNA replication:
    • DNA polymerase III
    • DNA helicase
    • DNA ligase
    • Primase
    • Single-strand binding proteins
    • Topoisomerase
    • DNA ligase