Prokaryote DNA Replication Flashcards
Q: What is the origin of replication in prokaryotic DNA replication, and how many origins are typically present?
A: In prokaryotic DNA replication, the origin of replication is a specific sequence where replication begins, known as the oriC in E. coli. Prokaryotes typically have a single origin of replication on their circular DNA.
Q: Which enzyme initiates DNA replication in prokaryotes by unwinding the DNA double helix?
A: DNA helicase unwinds the DNA double helix by breaking the hydrogen bonds between the two strands, creating a replication fork.
Q: What role does DNA primase play in prokaryotic DNA replication?
A: DNA primase synthesizes a short RNA primer that provides a 3’-OH group for DNA polymerase III to begin adding DNA nucleotides.
Q: Which enzyme is primarily responsible for synthesizing the new DNA strand in prokaryotes, and in which direction does it synthesize?
A: DNA polymerase III is primarily responsible for synthesizing the new DNA strand in prokaryotes, adding nucleotides in the 5’ to 3’ direction.
Q: How does DNA polymerase III ensure the accuracy of DNA replication?
A: DNA polymerase III has 3’ to 5’ exonuclease activity that allows it to proofread and remove incorrectly paired nucleotides, ensuring high fidelity in DNA replication.
Q: What is the function of DNA polymerase I in prokaryotic DNA replication?
A: DNA polymerase I removes RNA primers via its 5’ to 3’ exonuclease activity and fills in the gaps with DNA nucleotides.
Q: What enzyme seals the gaps between Okazaki fragments on the lagging strand during prokaryotic DNA replication?
A: DNA ligase seals the gaps between Okazaki fragments on the lagging strand by forming phosphodiester bonds between adjacent nucleotides.
Q: What is the difference between the leading and lagging strands in prokaryotic DNA replication?
A: The leading strand is synthesized continuously in the 5’ to 3’ direction toward the replication fork, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments, also in the 5’ to 3’ direction but away from the replication fork.
Q: What role do single-stranded binding proteins (SSBs) play during DNA replication?
A: Single-stranded binding proteins (SSBs) bind to and stabilize the single-stranded DNA exposed by helicase, preventing the DNA strands from reannealing or forming secondary structures.
Q: Which enzyme relieves the supercoiling tension ahead of the replication fork during prokaryotic DNA replication?
A: DNA gyrase (a type of topoisomerase II) relieves the supercoiling tension ahead of the replication fork by introducing negative supercoils.
