Question

Explain the contribution of Thermus aquaticus in the amplification of a gene of interest.

Answer 1

Thermus aquaticus is a bacterium whose heat-stable DNA polymerase (Taq polymerase) is used in PCR. PCR was developed by Kary Mullis in 1983.

Steps involved in PCR:

1. Denaturation: The DNA is heated to about 98°C to separate the two strands of double-stranded DNA.
2. Annealing: The temperature is lowered to about 60°C, allowing primers to bind to complementary sequences on the DNA strands.
3. Extension: At about 72°C, Taq DNA polymerase adds nucleotides to the primers and synthesises new DNA strands using the four types of deoxyribonucleotides.

These three steps are repeated for several cycles. Ideally, the number of DNA copies doubles in each cycle.

After 20 cycles:

2²⁰ = 1,048,576 ≈ 10⁶ copies

Since Taq polymerase is heat-stable, it remains active even after repeated heating and does not need to be added again after each cycle.