DNA Replication: The Role of Primers
What is the function of the "primer" in DNA replication?
a. The primer is a short RNA strand that supplies the 3' end required for DNA polymerases
b. The primer is the protein complex that binds to the origin of replication
c. The primer is a short piece of DNA made by primase
d. The primer is a short piece of DNA synthesized on the lagging strand, also known as an "Okazaki fragment"
Answer:
The primer is a short piece of RNA synthesized on both the leading and lagging strands during DNA replication.
During DNA replication, the primer plays a crucial role in initiating the synthesis of new DNA strands. It is necessary because DNA polymerase, the enzyme responsible for creating these strands, cannot start the process on its own. The primer acts as the starting point by providing a short sequence of RNA nucleotides that are complementary to the DNA template strand.
Once the primer is in place, DNA polymerase begins extending the strand, adding new nucleotides based on the template strand. On the lagging strand, where replication occurs discontinuously, multiple primers are used to create short DNA segments called Okazaki fragments. These fragments are later joined together by the enzyme DNA ligase to form a continuous DNA strand.
In contrast, the leading strand only requires one primer for continuous replication. By providing a starting point for DNA synthesis, primers ensure that DNA replication proceeds accurately and efficiently.