Q7 / 200 · MHT CET - Medical 2026 (26 April Shift 1) · Biology
During PCR cycle, the temperature range in the step of annealing is __________.
- Correct answerA$40 - 60\ ^\circ\text{C}$
- B$70 - 75\ ^\circ\text{C}$
- C$90 - 98\ ^\circ\text{C}$
- D$65 - 85\ ^\circ\text{C}$
Solution
Polymerase Chain Reaction (PCR) involves three main steps in each cycle:
1. Denaturation: The double-stranded DNA is heated to $90 - 98\ ^\circ\text{C}$ to separate it into two single strands.
2. Annealing: The temperature is lowered to $40 - 60\ ^\circ\text{C}$ to allow the oligonucleotide primers to attach (anneal) to their complementary sequences on the single-stranded template DNA.
3. Extension: The temperature is raised to $70 - 75\ ^\circ\text{C}$ (usually $72\ ^\circ\text{C}$), which is the optimum temperature for Taq DNA polymerase to synthesize the new DNA strand.
Therefore, the temperature range for the annealing step is $40 - 60\ ^\circ\text{C}$.
Answer: $40 - 60\ ^\circ\text{C}$
1. Denaturation: The double-stranded DNA is heated to $90 - 98\ ^\circ\text{C}$ to separate it into two single strands.
2. Annealing: The temperature is lowered to $40 - 60\ ^\circ\text{C}$ to allow the oligonucleotide primers to attach (anneal) to their complementary sequences on the single-stranded template DNA.
3. Extension: The temperature is raised to $70 - 75\ ^\circ\text{C}$ (usually $72\ ^\circ\text{C}$), which is the optimum temperature for Taq DNA polymerase to synthesize the new DNA strand.
Therefore, the temperature range for the annealing step is $40 - 60\ ^\circ\text{C}$.
Answer: $40 - 60\ ^\circ\text{C}$
Hence, the correct answer is option: 'A'.