Polymerase chain reaction (PCR)पॉलीमरेज़ शृंखला अभिक्रिया (PCR)
NCERT Fig 9.6 · Class 12 Biology · Chapter 9 · interactive diagram
Parts and their functions
- Template DNA (टेम्पलेट DNA) — The double-stranded DNA that carries the gene (region) to be copied.
- Region to be amplified (प्रवर्धित होने वाला भाग) — The gene of interest — only this stretch (between the two primers) is copied again and again.
- Denaturation (विकृतीकरण) — High temperature separates the two DNA strands.
- Primers (प्राइमर) — Small, chemically synthesised oligonucleotides complementary to the ends of the region; they bind (anneal) and give a starting point to the polymerase.
- Taq DNA polymerase (Taq DNA पॉलीमरेज़) — Thermostable DNA polymerase from the bacterium Thermus aquaticus; it stays active at the high temperature used for denaturation.
- Extension — new strands (विस्तार — नए रज्जुक) — The polymerase extends the primers using the nucleotides provided and the genomic DNA as template.
- Amplified copies (प्रवर्धित प्रतियाँ) — Each cycle doubles the DNA; repeated many times the segment is amplified about a billion times.
Steps
- Start: double-stranded DNA with the region (gene) we want to copy.
- ① Denaturation: high temperature separates the two strands.
- ② Annealing: two primers bind to the ends of the region on opposite strands.
- ③ Extension: Taq polymerase extends the primers and makes new strands.
- Repeat: every cycle doubles the DNA — about a billion copies after many cycles.
Original diagram drawn by Simple Learning Hub, based on NCERT Fig 9.6. Report a mistake