Final answer:
The synthesis of a new strand begins with the synthesis of an RNA primer complementary to a preexisting DNA strand. This RNA primer provides the starting point for DNA polymerase to add new nucleotides.
Step-by-step explanation:
The synthesis of a new strand begins with the synthesis of an RNA primer complementary to a preexisting DNA strand. This RNA primer provides the starting point for DNA polymerase to add new nucleotides. The new DNA strand synthesized in the direction of the replication fork is called the leading strand, while the new DNA strand synthesized in short pieces called Okazaki fragments in the opposite direction is called the lagging strand.