During DNA replication, which enzyme initiates DNA synthesis by creating a short RNA segment (primer) that provides a free $3\prime OH$ group for DNA polymerase?

• A. Primase
• B. DNA ligase
• C. DNA polymerase III
• D. Helicase

Answer: (A)

Verified step by step guidance

1. Understand the role of each enzyme listed in the problem during DNA replication.
2. Recall that DNA polymerase cannot start DNA synthesis on its own because it requires a free 3\' OH group to add nucleotides.
3. Identify the enzyme that synthesizes a short RNA primer to provide this free 3\' OH group; this enzyme is called primase.
4. Recognize that DNA ligase is responsible for joining Okazaki fragments, not initiating synthesis.
5. Note that helicase unwinds the DNA double helix, and DNA polymerase III extends the DNA strand but does not initiate it.