The Polymerase Chain Reaction (PCR) is one of the most commonly used techniques in the field of molecular biology and biotechnology. One way to look at PCR is that it is targeted DNA replication in vitro or in a test tube. Below, which reagents are required for PCR but NOT required for in vivo DNA replication.

A. DNA ligase

B. Deoxynucleotide triphosphates (dNTPs)

C. Helicase

D. DNA polymerase

E. Topoisomerase

F. Template DNA

G. DNA Primers

DNA primers

Explanation:

PCR uses short DNA segments called as primers. These primers become paired with the template DNA strands and are being elongated by the DNA polymerase enzyme (Taq polymerase). On the other hand, in vivo DNA replication does not use the DNA primers. Primase is the enzyme that makes RNA primers with free 3' OH end which is then elongated by DNA polymerases. The RNA primers are synthesized when the primase enzyme makes a short RNA copy of the DNA template strand.