Question

Place the Polymerase Chain Reaction events listed below in the order in which they occur. - Double-stranded DNA is produced - DNA sample is heated - Test tube with DNA sample is placed in machine - Taq polymerase initiates DNA synthesis - DNA denatures

Answer 1

1- Test tube with DNA sample is placed in machine

2- DNA sample is heated

3- DNA denatures

4- Taq polymerase initiates DNA synthesis

5- Double-stranded DNA is produced

Explanation:

The Polymerase Chain Reaction (PCR) is a technique widely used in molecular biology laboratories in order to produce many copies of a specific DNA sample. Thermocyclers are machines designed for a cyclic temperature change of the PCR. First, an initial denaturation step where DNA sample is heated to separate the double-stranded DNA into two single strands. Subsequently, 20-40 PCR cycles are repeated to produce millions of copies of a specific DNA sequence. There are three steps in each PCR cycle: 1-Denaturation to 94–98 °C (DNA strands are separated), 2-Annealing to 50–67 °C (primers bind to each DNA strand on the opposite ends of the DNA strands to be copied) and 3-Extension to 75–80 °C (Taq polymerase initiates the synthesis of complementary DNA strands).