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Steps of DNA
replication
1. DNA
helicase (enzyme) unwinds the DNA. The junction between the
unwound part and the open part is called a replication
fork.
2. DNA
polymerase adds the complementary nucleotides and binds the
sugars and phosphates. DNA polymerase travels from the 3' to the 5'
end.
3. DNA
polymerase adds complementary nucleotides on the other side
of the ladder. Traveling in the opposite direction.
4. One side is
the leading strand - it follows the helicase as it
unwinds.
5. The other
side is the lagging strand - its moving away from the
helicase
Problem: it
reaches the replication fork, but the helicase is moving in the
opposite direction. It stops, and another polymerase binds farther
down the chain.
This process
creates several fragments, called Okazaki Fragments, that are
bound together by DNA ligase.
6. During
replication, there are many points along the DNA that are
synthesized at the same time (multiple replication forks). It would
take forever to go from one end to the other, it is more efficient
to open up several points at one time. |
