NEET2026BiologyChapterActual
During the amplification of a gene of interest using Polymerase Chain Reaction (PCR), the reaction mixture is briefly cooled to approximately 50^ C - 60^ C after an initial high-temperature treatment. Which of the following events takes place during this cooling phase?
Options
- ASeparation of the double-stranded template DNA into single strands
- BHybridization of oligonucleotide primers to the complementary regions of the template DNA
- CAddition of deoxynucleotides to the primer by a thermostable DNA polymerase
- DLigation of the newly synthesized DNA fragments to form a continuous strand
Correct answer
B. Hybridization of oligonucleotide primers to the complementary regions of the template DNA
Step-by-step solution
Polymerase Chain Reaction (PCR) involves three main steps: 1. Denaturation: The reaction mixture is heated to 94^ C - 96^ C to separate the double-stranded DNA into single strands. 2. Annealing: The mixture is cooled to 50^ C - 60^ C . This allows the oligonucleotide primers to hybridize (anneal) to their complementary sequences on the single-stranded template DNA. 3. Extension: The temperature is raised to 72^ C , allowing a thermostable DNA polymerase (like Taq polymerase) to add deoxynucleotides to the primers,