Which component provides the template for DNA polymerase to add nucleotides during leading strand synthesis?

• A. Parental DNA Template
• B. RNA Primer
• C. DNA Ligase
• D. Helicase

Answer: (A)

The process relies on DNA polymerase reading an existing DNA strand and adding bases that are complementary to that template. In leading strand synthesis, the template is the parental DNA strand, which guides which nucleotides get incorporated as the polymerase moves along. An RNA primer is needed to start synthesis by providing a 3' end to extend from, but it does not serve as the template for base pairing. Helicase and ligase perform other roles—unwinding the DNA and sealing nicks, respectively. So the template that directs nucleotide addition is the parental DNA strand.