DNA Replication: The Beginning of a New Strand

What is the role of an RNA primer in DNA replication?

a. amino acid primer

b. lipid primer

c. hydrophilic primer

d. DNA primer

e. RNA primer

Answer:

During DNA replication, each new strand begins with an RNA primer.

During DNA replication, each new strand begins with an RNA primer. Primase synthesizes these primers, which are later replaced by DNA nucleotides. DNA ligase then seals the strands with phosphodiester bonds.

During DNA replication, each new strand begins with an RNA primer. This occurs because DNA polymerase, the enzyme responsible for adding new nucleotides, can only add to an existing 3' end. An enzyme called primase synthesizes a short RNA primer that is complementary to the DNA strand, providing the necessary 3'-OH group for DNA polymerase to begin adding DNA nucleotides. As replication progresses, a single primer is required for the leading strand, while the lagging strand, which is formed in short Okazaki fragments, needs a new primer for each fragment. After the DNA strand is elongated, the RNA primers are replaced with DNA, and DNA ligase seals the DNA strands by creating phosphodiester bonds.