AAMC FL Practice Exam

What is the role of primase in DNA replication?

1. To synthesize DNA strands

2. To unwind the DNA helix

3. To synthesize RNA primers

4. To repair DNA errors

The correct answer is: To synthesize RNA primers

Primase plays a crucial role in DNA replication by synthesizing short RNA primers that are necessary for DNA polymerases to initiate the synthesis of new DNA strands. During the process of replication, DNA polymerase cannot begin synthesis on its own; it requires a primer to provide a free 3' hydroxyl group to which nucleotides can be added. The RNA primers, created by primase, serve as starting points for DNA polymerases, allowing them to elongate the new DNA strands. The significance of RNA primers is especially evident in the context of the leading and lagging strands during DNA replication. On the leading strand, a single primer is synthesized, enabling continuous replication as the fork opens up. On the lagging strand, multiple primers are synthesized at intervals, allowing for the production of Okazaki fragments, which are subsequently joined together to form a continuous DNA strand. Understanding the function of primase illuminates its essential role in ensuring that DNA replication is initiated properly, which is foundational for the transmission of genetic information during cell division.