How scientists cut, join and copy genes to make useful products
Biotechnology uses living organisms or their parts to make useful products. Recombinant DNA technology begins with restriction enzymes, molecular scissors that cut DNA at specific palindromic sequences, such as EcoRI. The gene of interest and a vector, such as a plasmid, are cut with the same enzyme so their sticky ends match, and DNA ligase joins them. The recombinant DNA is introduced into a host such as E. coli, and selectable markers like antibiotic-resistance genes identify transformed cells.
The polymerase chain reaction (PCR) copies a DNA segment millions of times through repeated cycles of denaturation, primer annealing and extension by a heat-stable Taq polymerase. Gel electrophoresis separates DNA fragments by size. Products are grown on a large scale in bioreactors and then purified in downstream processing. Applications include human insulin made in bacteria, Bt cotton that produces an insecticidal protein, RNA interference to protect tobacco from nematodes, gene therapy for disorders like ADA deficiency and molecular diagnosis using PCR and ELISA.
Why it matters
Biotechnology has given diabetics safe human insulin, enabled rapid PCR tests for infections, and produced pest-resistant crops that reduce pesticide use. DNA fingerprinting helps solve crimes and settle paternity cases. It also raises ethical questions about genetically modified organisms and biopiracy, which societies regulate through bodies such as India’s GEAC.
Key terms
- Restriction enzyme
- An enzyme that cuts DNA at a specific recognition sequence.
- Vector
- A DNA molecule, such as a plasmid, used to carry a foreign gene into a host cell.
- PCR
- A technique that makes many copies of a specific DNA segment through repeated heating and cooling cycles.
- Transgenic organism
- An organism whose DNA has been altered by inserting a gene from another species.