DNA ReplicationCopying the genetic code
Copying the genetic codeDNA Replication
Unpack the Chromosomes
Unzip the DNA
Base pairing at the replication fork
Leading strand vs Lagging strand
Making Copies
Making Copies
copycopied during cell division
Sister Chromatids(identical copies)
Accessing the DNAin
activ
e D
NA
(dea
ctiva
ted
or m
itotic
)
DNA in use
Visualization of DNA Packing
For this video, visit:http://www.hhmi.org/biointeractive/dna/DNAi_packaging_vo2.html
Accessing the DNA
Accessing the DNA
DNA Structure
Complementary Base Pairing
Identical Parent and Daughter Strands
Replication Bubbles
helicase
5’
3’
3’
5’
Replication Bubbles
5’
3’
3’
5’
Replication Bubbles
5’
3’
3’
5’
Replication Bubbles
copies
Replication Fork
Replication Fork
5’
3’
3’
5’
Replication Bubbles
Releasing the Tension
Releasing the Tension Topoisomerase (gyrase) cleaves and uncoils DNA ahead of helicase Single-stranded DNA binding proteins (SSB) prevent DNA from
coiling back up
DNA Replication
Primase
RNA primer
DNA Polymerase III
5’
3’
3’
5’
DNA Replication
The leading strands grow toward the replication fork PROBLEM: DNA polymerase III only works in the
5’-3’ direction.
Leading Strands5’
3’
3’
5’
DNA Replication
5’
3’
3’
5’
DNA Replication
Lagging Strands
The lagging strands grow away from the replication fork
5’
3’
3’
5’
DNA Replication
5’
3’
3’
5’
DNA Polymerase IDNA Ligase
DNA Replication
5’
3’
3’
5’
DNA Replicationcontinuous & discontinuous
Okazaki Fragments
5’
3’
3’
5’
DNA Polymerase moves in a 5’ - 3’ direction
5’-3’ chain synthesized continuously
3’-5’ chain synthesized discontinuously
Results in a series of Okazaki fragments
Later sealed up by DNA ligase
The Whole Process in 3D
For this video, visit: http://www.hhmi.org/biointeractive/dna
/DNAi_replication_schematic.html
The Whole Process in 3D
For this video, visit:http://www.hhmi.org/biointeractive/dna/DNAi_replication_vo2.html
Animations
DNA Replication: http://www.youtube.com/watch?v=4jtmOZaIvS0
McGraw-Hill: DNA Replication & Meselson-Stahl: http://highered.mcgraw-hill.com/sites/0072437316/st
udent_view0/chapter14/animations.html#
DNA Song: http://www.youtube.com/watch?v=dIZpb93NYlw
Credits
Molecule drawing created using ChemSketch.
Some from the Pearson or Nelson Biology 12 textbook.
Some images from Wikimedia Commons
Some from unknown sources.