Which enzyme is tasked with adding nucleotides during DNA chain elongation?

DNA polymerase III is the enzyme specifically responsible for adding nucleotides during the elongation phase of DNA replication. This enzyme plays a crucial role in synthesizing new DNA strands by catalyzing the formation of phosphodiester bonds between nucleotides. It works by adding nucleotides to the 3’ end of the growing DNA strand, extending it in a 5’ to 3’ direction.

During DNA replication, DNA polymerase III requires a primer, which is typically provided by primase. However, once the primer is in place, DNA polymerase III takes over the task of adding nucleotides to create the new complementary DNA strand. Its high processivity and ability to proofread the newly synthesized DNA also enhance the accuracy of replication.

While other enzymes mentioned in the options have important roles in DNA replication, such as DNA polymerase I, which removes RNA primers and replaces them with DNA, and DNA ligase, which seals nicks between Okazaki fragments on the lagging strand, they do not directly add nucleotides during the chain elongation process. Hence, DNA polymerase III is correctly identified as the enzyme tasked with elongating the DNA chain by incorporating nucleotides.