Q10 / 180 · NEET 2026 (Cancelled) · Botany
Identify the correct sequence of steps in each cycle of Polymerase Chain Reaction :
- AExtension $\rightarrow$ Annealing $\rightarrow$ Denaturation
- BAnnealing $\rightarrow$ Denaturation $\rightarrow$ Extension
- CDenaturation $\rightarrow$ Extension $\rightarrow$ Annealing
- Correct answerDDenaturation $\rightarrow$ Annealing $\rightarrow$ Extension
Solution
Polymerase Chain Reaction (PCR) involves three main steps in each cycle:
Denaturation: The double-stranded DNA is heated to a high temperature (around $94^{\circ}\text{C}$) to break the hydrogen bonds, resulting in two single strands.
Annealing: The temperature is lowered (around $50^{\circ}\text{C}$ to $65^{\circ}\text{C}$) to allow the primers to bind to the complementary sequences on the single-stranded DNA.
Extension: The temperature is raised (around $72^{\circ}\text{C}$) to allow Taq polymerase to synthesize the new DNA strand by adding nucleotides to the primers.
Thus, the correct sequence is Denaturation $\rightarrow$ Annealing $\rightarrow$ Extension.
Answer: Denaturation $\rightarrow$ Annealing $\rightarrow$ Extension
Denaturation: The double-stranded DNA is heated to a high temperature (around $94^{\circ}\text{C}$) to break the hydrogen bonds, resulting in two single strands.
Annealing: The temperature is lowered (around $50^{\circ}\text{C}$ to $65^{\circ}\text{C}$) to allow the primers to bind to the complementary sequences on the single-stranded DNA.
Extension: The temperature is raised (around $72^{\circ}\text{C}$) to allow Taq polymerase to synthesize the new DNA strand by adding nucleotides to the primers.
Thus, the correct sequence is Denaturation $\rightarrow$ Annealing $\rightarrow$ Extension.
Answer: Denaturation $\rightarrow$ Annealing $\rightarrow$ Extension
Hence, the correct answer is option: 'D'.