Which of the following molecules is not required for a PCR reaction? View Available Hint(s) Which of the following molecules is not required for a PCR reaction? DNTPs Ligase Primer DNA Submit Part B The thermostability of Taq polymerase is required during the annealing phase of PCR. View Available Hint(s) The thermostability of Taq polymerase is required during the annealing phase of PCR. True False Submit Part C What is the purpose of raising the temperature to 90–95°C at the beginning of each cycle of PCR? View Available Hint(s) What is the purpose of raising the temperature to 90–95°C at the beginning of each cycle of PCR? To separate the double‑stranded DNA To renature two single DNA strands To extend the primer To attach the primer

A Ligase

B False

C To separate the double‑stranded DNA

Explanation:

The Polymerase Chain Reaction (PCR) is a technique widely used in molecular biology laboratories in order to make millions of copies of a specific sequence of DNA. PCR requires deoxynucleotide triphosphates (dNTPs) to synthesize new copies of the target DNA fragment, a thermostable DNA polymerase that adds nucleotides to new DNA strands, and primers that attach to complementary ends at each DNA strand. PCR has three phases: 1-Denaturation, where the double-stranded DNA molecule is heated to separate it into two single (separated) strands; 2-annealing, where the temperature is lowered in order to allow the primers to attach each DNA strand, and 3- extension, where the temperature is increased (again), and the thermostable DNA polymerase adds the appropriate dNTPs to new DNA strands. In consequence, annealing occurs at the lowest temperature. Moreover, during the denaturation stage, the temperature is increased at 90–95°C  in order to denature the DNA strands into single strands.

a physical change is being made.