Primase

The enzyme that initiates DNA* replication by adding a short three to ten base long RNA primer to the template strand. The priming sequence provides the 3’ hydroxyl end needed for DNA polymerase* to being synthesizing DNA. 

The addition of an RNA priming sequence complicates the replication process. The RNA nucleotides* in the priming sequence need to be replaced by DNA nucleotides before the completion of replication.