What type of nucleotides can DNA polymerase III add to during DNA synthesis?

DNA polymerase III is an essential enzyme in prokaryotic DNA replication responsible for synthesizing new DNA strands by adding nucleotides. It can only add nucleotides to an existing strand that has a free -OH (hydroxyl) group at the 3' end. This requirement is crucial because DNA polymerases catalyze the formation of phosphodiester bonds between nucleotides, and this reaction involves the 3' -OH of the growing DNA strand attacking the phosphate group of the incoming nucleotide.

When DNA polymerase III synthesizes new DNA, it can work on both the leading and lagging strands. However, its ability to add nucleotides depends on there being a free -OH group present to extend from, which narrows the scenarios under which it can operate.

The correct choice acknowledges that DNA polymerase III can only add nucleotides when there is an existing strand with a free -OH at the 3' end, which is why this answer is accurate. The other options misinterpret the functional requirement for nucleotide addition by suggesting conditions under which DNA polymerase III would not be able to function correctly.