The top strand is the template DNA and the bottom strand sho

The top strand is the template DNA, and the bottom strand shows the lagging strand prior to the action of DNA polymerase I. The lagging strand contains three Okazaki fragments. The RNA primers, which are shown in red, have not yet been removed. A: Which Okazaki fragment was made first, the one on the left or the one on the right? B Which RNA primer would be the first one to be removed by DNA polymerase I, the primer on the left or the primer on the right? C For this primer to be removed by DNA polymerase I and for the gap to be filled in. is it necessary for the Okazaki fragment in the middle to have already been synthesized? Explain D. Let\'s consider how DNA ligase connects the left Okazaki fragment with the middle Okazaki fragment After DNA polymerase I removes the middle RNA primer and fills in the gap svelte DNA, where does DNA ligase function with respect to the arrows on either side of the middle RNA primer? In other words is ligase needed at the left arrow, at the right arrow or both? E. Does DNA ligase need to use ATP as a source of energy to catalyze a reaction? Explain why or why not.

Solution

Answer:

Part A). The one on the right

Because, it is farthest away fromthe replication fork

Part B). The primer on the right

The RNA primer in the right Okazaki fragment would be removed first. Because the DNA polymerase would begin by elongating the DNA strand of the middle Okazaki fragment and removing the right RNAprimer with its 5\' to 3\' exonuclease activity.

Part C).

Yes, If the middle fragment was not present, DNA polymerase could not fill in this DNA (because it needs a primer).

Part D).

DNA ligase only at the right arrow. DNA polymerase I begins at the end of the left Okazaki fragment and synthesizes DNA to fill in the region as it removes the middle RNA primer. DNA polymerase I is simply extending the length of the left Okazaki fragment.

Part E). DNA ligase use ATP as an energy source, ligase catalyzes a reaction in which the phosphate group sticking off the 5’ end of one DNA strand is linked to the hydroxyl group sticking off the 3’ end of the other. This reaction produces an intact sugar-phosphate backbone.