Polymerase chain reaction amplifies DNA through repeated heating and cooling cycles.
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The polymerase chain reaction amplifies a specific DNA segment exponentially through repeated heating and cooling cycles. Each cycle has three steps: denaturation near 95 C separates the strands, annealing at roughly 55 to 65 C lets short primers bind their complementary sequences, and extension at about 72 C lets a heat-stable polymerase such as Taq build new strands. Because the product doubles every cycle, about 30 cycles can give roughly a billion copies from a single template. PCR is used in diagnostics, forensic profiling, cloning and detection of viruses such as SARS-CoV-2. Kary Mullis received the Nobel Prize in Chemistry in 1993 for the invention.
Key ideas: Polymerase chain reaction amplifies DNA exponentially: copies equal 2 to the n after n cycles, so 30 cycles give about 10 to the 9 copies. Cycle steps: denature about 95 C, anneal primers 50 to 65 C, extend about 72 C with heat-stable Taq polymerase. Needs template, two primers, dNTPs, Mg2+ and buffer.
Common mistakes and connections: Mistake: expecting exact doubling at every cycle, the real plateau comes when reagents run out. Wrong annealing temperature gives nonspecific products. Contamination is the major practical problem. Links to DNA replication, forensic fingerprinting and diagnostic tests such as RT-PCR for RNA viruses.
The target doubles every cycle, so copies grow as 2 to the n. By 30 cycles one template gives roughly a billion copies. The interactive lesson shows this as a live animation or chart.
Thirty cycles starting from one template molecule give 2 to the power 30, or about a billion, copies.
Polymerase chain reaction amplifies DNA through repeated heating and cooling cycles.
PCR is a advanced topic in Biochemistry, Environment & Industry. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Biochemistry, Environment & Industry first: DNA Replication, Transcription and Translation, Genetic Code.
The next topics in Biochemistry, Environment & Industry are CRISPR and Metabolism.
Yes. The interactive lesson includes a self-check question on PCR, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.
PCR is topic 29 of 127 in Biochemistry, Environment & Industry.
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