Final answer:
The correct order of the PCR steps is Denaturation, Denaturation, Annealing, Annealing, and Extension. This sequence reflects the repeated cycle of the PCR process, encompassing the separation of DNA strands, primer annealing, and DNA synthesis.
Step-by-step explanation:
The correct order for the first five thermocycler steps in a PCR run is as follows:
Denaturation (Step D)
Denaturation (Step A)
Annealing (Step B)
Annealing (Step E)
Extension (Step C)
This order reflects the repeating cycle of a PCR process, which begins with denaturation, where the double-stranded DNA is heated to around 95°C to separate the strands. Next, during annealing, the temperature is lowered to approximately 55°C to allow the primers to attach to each single strand. Finally, in the extension step, the temperature is increased to about 72°C to enable the DNA polymerase to synthesize the new strand of DNA from the primer.