when rna creates a copy of the select strand it needs, it is called
This unzipping takes place in both directions from the replication origins, creating a replication bubble. The replication is therefore said to be bi-directional. Once the two strands are separated a small piece of RNA, called an RNA primer, is attached to the DNA by an enzyme called DNA primase. These primers are the beginnings of all new DNA chains since the enzyme responsible for the copying of the DNA, DNA polymerase, can not start from scratch.