DNA synthesis is performed by the enzyme DNA polymerase. However, DNA polymerase requires the presence of a free 3' OH on the existing DNA or RNA segment. The enzyme primase forms small RNA segments that serve as primers. Primers are formed by using the DNA template strands and have free 3' OH ends. DNA polymerase extends the primers by adding deoxyribonucleotides according to the sequence of the DNA template strand. Therefore, DNA polymerases are the enzymes of primer elongation.
