Download Ch. 12 DNA Replication and Recombination

Chapter 12
Topics
Models of Replication
Prokaryotic and Eukaryotic Replication
Models of Recombination: read pp 339-342
Three Models of DNA Replication
Which is correct?
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#
DATA TO SUPPORT SEMI-CONSERVATIVE MODEL
Prokaryotic Replication
E.coli 4.7 million bp
Bacteria can double every 20 minutes at a rate of 1000
nucleotides/second!
2 models of Prokaryotic Replication
The Theta Model
Rolling Pin Model
θ
Theta Replication
Radioactive labeled prokaryotic DNA
Rolling Pin Model
Occurs in viruses and factor F
Prokaryotic Mechanism of
Replication
An: overview
of E. coli
replication
Bacterial Mechanism of Replication
oriC
Key concepts & Proteins
Step 1. Initiation
helicases
Step 2. Unwinding: Helicase
Disease of Aging: Werner’s Disease
In eukaryotic cells: helicase mutation has
been related to “Werner’s Disease.
Notice: Replication Bubble Forms
Helper proteins
Notice: Directionality
Helper proteins
SUMMARY
Prokaryotic DNA replication
Leading strand
Lagging strand
Prokaryotes Polymerases
The major players are:

Pol l

Pol II

Pol III


Pol IV
Pol V
Removes/replaces primers
repair
ELONGATION: step 4
repair
Step 5. Ligation

Ligase
These darn Okazaki
Fragments!
Step 6. Termination

A certain DNA sequence may

A protein may physically
replication
replication
SUMMARY
Prokaryotic DNA replication
Leading strand
Lagging strand
http://www.johnkyrk.com/DNAreplication.html
Animation of Elongation
Nucleotide
polymerization
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#
How are mistakes avoided?

By: Nucleotide selection

By: Proofreading

By: Mismatch Repair
Fidelity of DNA replication

Only 1 mistake per billion nucleotides!
Eukaryotic Replication
A human chromosome about 100 million bp
Replication occurs in minutes to hours!
Can you notice a difference between this replication
process vs bacterial replication?
Answer: Numerous replication
origins.
5’ to 3’ replication occurs in eukaryotes just like in our bacterial friends.
Prokaryotic and Eukaryotic
Replication are similar but there are
some differences; these include…
Origins “get tagged” by
a replication licensing factor.
Eukaryotic DNA Polymerases
There are more and different DNA polymerases.


DNA Pol
DNA pol
α

Priming & replication
δ

Replication
Repair & recombination
(RNA polymerase)
ß
DNA pol
β


DNA pol
ε

Repair and replication
γ

Mitochondrial DNA replication

DNA pol
Nucleosome Assembly
Unique to eukaryotic replication process
What happens when you reach the
end of linear DNA?
Oops a problem at
the end!!
http://faculty.plattsburgh.edu/donald.slish/Telomerase.html
Telomeres and Telomerase!
Are loss of telomeres
related to aging?
Or is too much
telomerase
activity related cancer?
Cells with telomerase activity
Embryonic cells
Intestinal cells
And bone marrow
Assignment please read: pp 335339
The Holliday Model of DNA recombination