Unit 3-Molecular Genetics Lesson 2 2.0 Flashcards
What initiates DNA replication?
Replication begins in 2 directions from the ori as a region of the DNA is unwound.
Which direction does DNA replication proceed on the leading strand?
Towards the direction of the replication fork.
Which direction does DNA replication proceed on the lagging strand?
Away from the replication fork.
What forms when 2 replication forks are too near in eukaryotes?
A replication bubble.
Why can’t DNA polymerase start incorporating nucleotides on its own?
It needs an existing 3’ end of a nucleic acid.
What provides the 3’ end required for DNA polymerase?
A short segment of RNA called a primer.
What synthesizes the RNA primer?
RNA primase.
In which direction does DNA polymerase III add nucleotides?
In the 5’ to 3’ direction of the new strand.
Where do free bases float during DNA synthesis?
In the nucleoplasm as deoxyribonucleoside triphosphates.
What provides the energy for DNA synthesis?
Hydrolyzing the bond between the 1st and 2nd phosphates of the deoxyribonucleoside.
What is the junction called where the two DNA strands are still joined?
The replication fork.
How is the leading strand built during elongation?
Continuously toward the replication fork.
How is the lagging strand built during elongation?
Discontinuously in short fragments known as Okazaki Fragments.
What enzyme is responsible for removing RNA primers and joining Okazaki fragments?
DNA ligase.
What is a limitation of DNA polymerase on the lagging strand?
It cannot replicate the very end of the lagging strand due to lack of a 3’ OH- group.
