Question 1

How does DNA replication begin in prokaryotes?

Accepted Answer

DNA replication in prokaryotes initiates at the origin of replication, where DNA helicases unwind the double helix to create a replication fork. This unwinding exposes single-stranded DNA templates that serve as the basis for new strand synthesis. The process requires coordinated action of multiple enzymes to proceed efficiently.

Question 2

What is the role of single-strand DNA binding proteins during prokaryotic replication?

Accepted Answer

Single-strand DNA binding proteins coat exposed single-stranded DNA to prevent it from re-annealing or forming secondary structures. These proteins stabilize the template strands, allowing DNA polymerase and other replication machinery to access the DNA efficiently. They remain bound until the complementary strand is synthesized.

Question 3

Why do prokaryotes have both leading and lagging strand synthesis?

Accepted Answer

DNA polymerase synthesizes DNA only in the 5' to 3' direction, but the two strands of the double helix run antiparallel. The leading strand is synthesized continuously toward the replication fork, while the lagging strand is synthesized discontinuously as Okazaki fragments away from the fork. This asymmetry accommodates the directional constraint of DNA polymerase.

Question 4

What is the function of DNA topoisomerases in prokaryotic replication?

Accepted Answer

DNA topoisomerases relieve the tension created by unwinding the double helix ahead of the replication fork. As helicases separate the strands, positive supercoiling accumulates downstream. Topoisomerases cut and rejoin DNA strands to release this tension, allowing replication to proceed without mechanical obstruction.

Question 5

How does the replisome coordinate multiple enzymes during prokaryotic DNA replication?

Accepted Answer

The replisome is a multi-protein complex that assembles at the replication fork and coordinates the activities of helicases, primase, DNA polymerase, and other enzymes. This coordinated assembly ensures efficient and accurate DNA synthesis on both strands. The replisome components and the trombone model describe how the lagging strand template loops to maintain coordination.

Question 6

What distinguishes prokaryotic genome replication from eukaryotic replication?

Accepted Answer

Prokaryotes have circular chromosomes with a single origin of replication, while eukaryotes have linear chromosomes with multiple origins. Prokaryotic replication is faster and simpler, lacking the telomere end-replication problem. Comparing mitochondrial, chloroplast, and prokaryotic genomes reveals that prokaryotic DNA replication is more similar to organellar replication than to nuclear eukaryotic replication.

Question 7

How do prokaryotes ensure accurate DNA replication?

Accepted Answer

Prokaryotic DNA polymerase possesses 3' to 5' exonuclease activity, allowing it to remove incorrectly paired nucleotides immediately after incorporation. This proofreading mechanism, combined with mismatch repair systems, maintains high fidelity during replication. The accuracy of base pairing and its significance in DNA replication ensures that genetic information is faithfully transmitted to daughter cells.

Prokaryotlarda Replikasyon

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