Primase: Definition & Function

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  • 0:03 Primase
  • 0:23 DNA Replication
  • 1:13 Primase Function
  • 2:04 Necessity of Primase
  • 2:46 DNA & RNA
  • 3:05 Lesson Summary
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Lesson Transcript
Instructor: Katie Chamberlain

Katie has a PhD in Microbiology and has experience preparing online education content in Biology and Earth Science.

Primase is a really important part of DNA replication. In this lesson, you'll learn about DNA replication, the role primase plays in it, and why primase is necessary.


Primase is an enzyme that creates a primer on a DNA strand by adding RNA nucleotides to the strand according to the DNA template sequence. This process occurs during DNA replication. If all this sounds complicated, don't worry. We'll break it down below, starting with how DNA replication works.

DNA Replication

In order for an animal to grow or make new cells, it has to first make copies of those cells. Since DNA provides the blueprints for everything a cell needs to do, it has to be copied, too. The process of copying DNA is called DNA replication, and it occurs before cell division.

DNA has a double helix shape, like a zipper that's been twisted. In order to make two zippers out of one, the original zipper is unzipped and each side is used as a template. A new partner strand is synthesized based on this template.

The new strand must be built to exactly match up with its partner. Several enzymes are required to minimize the number of mistakes, or mutations, in the DNA. The specifics of this can be found in another lesson - just know that it is a complicated process.

Primase Function

After the DNA is unzipped, by an enzyme called helicase, it is time for primase to come in. Primase starts off the creation of the new strand of DNA by adding the first nucleotide building blocks at a site called the origin of replication. This will be the starting point for creating the new side of the DNA zipper.

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