Molecular biologyLesson 3 of 4 in the course DNA Structure and Function

Prokaryotic DNA Replication: Initiation and Strand Synthesis

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Prokaryotic DNA replication begins at a specific place on the chromosome and proceeds rapidly in both directions. This lesson explains how the replication machinery identifies where to start, opens the DNA, and keeps the exposed strands ready for copying.

DNA replication starts at specific DNA sequences called origins of replication. Proteins recognize and bind to these sequences, helping assemble the machinery needed to copy the chromosome.

All flashcards

What is an origin of replication?
A particular DNA sequence recognized by proteins where the replication machinery begins copying DNA.
How does replication proceed from the *E. coli* origin?
It proceeds bidirectionally: two replication forks form at the origin and move in opposite directions around the circular chromosome.
What is the role of helicase?
Helicase unwinds DNA by separating the two strands and breaking hydrogen bonds between paired nitrogenous bases. It uses energy from ATP hydrolysis.
What do single-strand binding proteins do?
They bind to exposed single-stranded DNA near replication forks, helping keep the strands separated so they do not rewind into a double helix.
How does topoisomerase help during DNA replication?
It relieves twisting strain ahead of a replication fork by making temporary cuts in DNA and then resealing the molecule.

Quiz questions

  1. Which enzyme is the main DNA-synthesizing enzyme during prokaryotic DNA replication?Answer: DNA polymerase III
  2. What provides the free 3′-OH group that DNA polymerase needs to begin extending a strand?Answer: An RNA primer
  3. How is the leading strand synthesized relative to the moving replication fork?Answer: Continuously toward the fork
  4. What are Okazaki fragments?Answer: Short DNA sections synthesized discontinuously on the lagging strand
  5. What does DNA polymerase I do during primer processing?Answer: Removes RNA primers and fills the resulting gaps with DNA

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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