Primers are described as which of the following in replication?

Primers are described as which of the following in replication?

• A. The components that must be synthesized to start replication are RNA primers
• B. Enzymes that build the DNA strand
• C. Proteins that separate the DNA strands
• D. Short RNA sequences with a 3' end that initiate replication

Answer: (D)

Primers provide the starting point for DNA synthesis by giving DNA polymerase a free 3' OH to extend from. They are short RNA sequences made by primase, positioned where replication should begin on each strand (one primer for the leading strand, and primers for each Okazaki fragment on the lagging strand). DNA polymerases can’t start from nothing; they must add onto an existing 3' end, so these short RNA primers are essential to initiate replication. After synthesis begins, the RNA primers are removed and replaced with DNA, and the fragments are joined. That’s why the description “short RNA sequences with a 3' end that initiate replication” best captures what primers are and what they do.

Primers provide the starting point for DNA synthesis by giving DNA polymerase a free 3' OH to extend from. They are short RNA sequences made by primase, positioned where replication should begin on each strand (one primer for the leading strand, and primers for each Okazaki fragment on the lagging strand). DNA polymerases can’t start from nothing; they must add onto an existing 3' end, so these short RNA primers are essential to initiate replication. After synthesis begins, the RNA primers are removed and replaced with DNA, and the fragments are joined. That’s why the description “short RNA sequences with a 3' end that initiate replication” best captures what primers are and what they do.