DNA polymerase builds the new strand in the 5’ to 3’ direction or the leading strand. However, the DNA polymerase in the 3’ to 5’ direction or the lagging strand is moving away from the helicase’s direction so it has to keep up to where the unwinding is happening. Primase needs to make primers for DNA polymerase to build. These fragments are known as okazaki fragments. Then, the primers have to get replaced with DNA bases since the primers are made up of RNA.