Polymerase chain reaction (PCR)
Polymerase chain reaction (PCR) is a laboratory technique used to amplify specific
DNA sequences, making millions to billions of copies
from a small initial sample. This process involves several key steps:
1. Denaturation:
The double-stranded DNA is heated to around 94-98°C to separate it into two single strands.
2. Annealing:
The temperature is lowered to 50-65°C to allow primers (short DNA sequences complementary to the target region) to
bind (anneal) to the single-stranded DNA.
3. Extension:
The temperature is raised to 72°C, the optimal temperature for DNA polymerase, an enzyme that extends the primers by adding nucleotides to form a new strand of DNA.
These steps are repeated for 20-40 cycles, exponentially increasing the number of DNA copies. This process results in the exponential amplification of the target DNA, making millions of copies from a small initial sample. PCR is essential in various applications, including genetic research, medical diagnostics, forensic science, and biotechnology.