Key Enzymes in Replication
What enzyme unzips the double helix during DNA replication?
Helicase
On the lagging strand, which direction does synthesis occur?
In the 5’ to 3’ direction, but in short segments (Okazaki fragments).
What is the function of the origin of replication?
It is the starting point where DNA replication begins.
What are Okazaki fragments?
Short DNA fragments synthesized on the lagging strand during DNA replication.
How does the lagging strand synthesis relate to leading strand synthesis?
Both occur simultaneously but in different directions. The leading strand is synthesized continuously, while the lagging strand is synthesized in fragments.
Which enzyme adds new nucleotides to the growing DNA strand?
DNA polymerase III
What causes the lagging strand to be synthesized in fragments?
DNA polymerase can only synthesize DNA in the 5' to 3' direction, so it must work backward relative to the replication fork, creating fragments.
What is the role of the replication fork in DNA replication?
The replication fork is where the two DNA strands are separated to allow replication to occur.
Why are Okazaki fragments important for lagging strand synthesis?
They allow the lagging strand to be synthesized in short bursts, overcoming the directionality problem of DNA polymerase.
After the Okazaki fragments are joined, which enzyme ensures that the new strand is complete?
DNA Ligase
What enzyme removes RNA primers and replaces them with DNA nucleotides?
Answer: DNA polymerase I
How is the RNA primer used in lagging strand synthesis?
The RNA primer provides a 3' hydroxyl group for DNA polymerase to begin synthesizing the Okazaki fragment.
Which strand is synthesized continuously during DNA replication?
The leading strand
How does the removal of RNA primers contribute to the formation of the lagging strand?
RNA primers are removed and replaced with DNA by DNA polymerase I, allowing the strand to be completed.
What happens when DNA polymerase I removes the RNA primer from the lagging strand?
The gap is filled with DNA nucleotides, and the strand becomes continuous.
Which enzyme seals the gaps between Okazaki fragments on the lagging strand?
DNA ligase
What happens to the RNA primer after its role is completed in lagging strand synthesis?
The RNA primer is removed by DNA polymerase I and replaced with DNA nucleotides.
What is the difference between the leading strand and the lagging strand?
The leading strand is synthesized continuously, while the lagging strand is synthesized in short Okazaki fragments.
How does DNA ligase contribute to Okazaki fragment formation?
DNA ligase connects the Okazaki fragments by sealing the gaps between them.
How does the replication machinery move forward during the synthesis of both strands?
The helicase unwinds the DNA, while the single-strand binding proteins stabilize the unwound strands, and the polymerase synthesizes the new strands.
What enzyme synthesizes the RNA primer required for DNA replication?
Answer: Primase
How are Okazaki fragments connected after they are synthesized?
DNA ligase connects the Okazaki fragments by forming phosphodiester bonds between them.
What is the purpose of DNA Replication?
To make a identical copy for cell division.
What is the fate of the Okazaki fragments once they are synthesized?
They are joined together by DNA ligase to form a continuous strand.
How does the entire replication process ensure the accuracy of DNA copying?
DNA polymerase has proofreading capabilities to correct errors, and mismatch repair systems fix any remaining mistakes after replication.