What happens during the extension phase of DNA replication?

During the extension phase of DNA replication, the key event is the synthesis of a new DNA strand. This phase follows the primer annealing, where short RNA primers serve as starting points for DNA synthesis. DNA polymerase, the enzyme responsible for synthesizing new DNA, binds to these primers and adds complementary nucleotides to the growing DNA strand, effectively elongating it based on the template strand.

The template strand, which serves as a guide for the synthesis, directs the sequence of nucleotides that DNA polymerase incorporates into the new strand. This process is critical for accurately replicating the genetic material of a cell, ensuring that each daughter cell inherits the correct genetic information.

The other options present activities that occur in different phases of DNA replication or do not accurately depict what happens during the extension phase. Primers are indeed removed later in the process during the replacement phase. The unwinding of the DNA template occurs prior to the extension phase and is a crucial step in preparing the DNA for replication. Separating the strands by increasing temperature is specific to processes like PCR, but this is not a characteristic of the extension phase during standard DNA replication.