At the replication fork, the template for the lagging strand is thought to loop around. This looping would allow the lagging-strand polymerase to move along with the rest of the replication fork instead of in the opposite direction. The single-strand part of the loop is bound by the single-strand DNA-binding (SSB) proteins. As each Okazaki fragment is synthesized toward completion, how does the size of the loop change? What about the size of the SSB-bound part of the loop?
A) Increases; increases.
B) Increases; decreases.
C) Decreases; increases.
D) Decreases; decreases.
E) Decreases; does not change.

Question

Quizplus · Accepted Answer

The double-strand region of the loop represents the growing Okazaki fragment and gradually increases in size. Additionally, as each Okazaki fragment is growing, the fork is also traveling, exposing more single-stranded DNA in the loop. The loop size resets to zero upon initiating the synthesis of the next Okazaki fragment.

At the Replication Fork, the Template for the Lagging Strand