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DNA replication
Is done with a system of enzymes.
1. Helicase
Binds to the origin breaks the hydrogen bond and unwinds the double helix.
This creates a replication fork.
DNA replication is going in both directions toward the replication fork.
2. Topoimerase
Every time there is supercoiling it makes a cut in the DNA to relieve supercoiling and it will ligate (rejoin) the two ends back together.
3. Single Stranded Binding Proteins
Stops hydrogen bonding to keep the DNA apart.
4. Primase
Makes short segments of RNA primer so DNA Polymerase III can start.
5. DNA polymerase III
Will make the new strand of DNA going 5' to 3' only.
6. DNA polymerase I
Cuts out the primer and fills in the gap with DNA.
7. DNA polymerase II
Has no known function.
8. DNA Ligase
Joins the two strand together.
DNA synthesis
Is always towards the replication fork.
The Leading Strand
Can be synthesized continuously in 5' to 3' direction.
The Lagging Strand
The direction is 3' to 5' so it cannot be synthesized continuously.
It's synthesized in short segments 5' to 3' called
Okazaki Fragments
.
The lagging strand is completed when an enzyme, DNA ligase fills in the spaces betweek Okazaki fragments with the correct nucleotides.
Author
Jess
ID
42797
Card Set
Microbiology
Description
The enzymes. The leading strand and lagging strand
Updated
2010-10-17T20:29:46Z
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