[Campbell Biology P.374] Which of the following correctly orders the events during the synth... | Practice Question

Which of the following correctly orders the events during the synthesis of an Okazaki fragment on the lagging strand, as depicted in Figure 16.17?

  • A: Primase adds RNA primer → DNA pol I replaces RNA with DNA → DNA ligase joins fragments.
  • B: DNA pol III adds DNA → Primase adds RNA primer → DNA ligase joins fragments.
  • C: Primase adds RNA primer → DNA pol III adds DNA nucleotides → DNA pol I replaces RNA with DNA → DNA ligase joins fragments.
  • D: Helicase unwinds DNA → DNA pol III adds DNA → Primase adds RNA primer.
  • E: DNA ligase joins fragments → DNA pol I replaces RNA with DNA → Primase adds RNA primer.

Explanation

The synthesis of an Okazaki fragment begins with primase synthesizing an RNA primer Step 1 , followed by DNA pol III adding DNA nucleotides to extend the fragment Steps 2 & 4 . After the fragment is formed, DNA pol I removes the RNA primer and replaces it with DNA Step 5 , and finally, DNA ligase joins the newly synthesized fragment to the adjacent one Step 6 .