Question
Describe principles of genetic engineering and their applications.
Answer
Genetic engineering (recombinant DNA technology) is the deliberate manipulation of an organism’s genetic material by introducing, deleting, or modifying specific DNA sequences, typically to produce a desired protein product or trait.
Principles/basic steps:
- Isolation of the gene of interest — obtained from genomic DNA, complementary DNA (cDNA, synthesized from mRNA using reverse transcriptase, avoiding introns), or chemically synthesized.
- Restriction enzyme digestion — sequence-specific restriction endonucleases cut both the gene of interest and a vector (plasmid, bacteriophage, or other carrier) at matching sites, often producing complementary “sticky ends.”
- Ligation — DNA ligase joins the gene of interest into the vector, forming a recombinant DNA molecule.
- Transformation/transfection — the recombinant vector is introduced into a suitable host cell (bacteria, yeast, or mammalian cells) via transformation (bacteria), transfection (eukaryotic cells), or transduction (phage-mediated).
- Selection — host cells that have taken up the recombinant vector are identified/selected, commonly using antibiotic-resistance marker genes carried on the vector.
- Expression and harvesting — the host cell’s own transcription/translation machinery expresses the introduced gene, producing the desired protein, which is then harvested and purified.
Key tools: restriction enzymes, DNA ligase, plasmid/phage vectors, PCR (for amplifying specific DNA sequences), and, more recently, CRISPR-Cas9 gene-editing technology (allowing precise, targeted modification of genomic sequences).
Applications:
- Recombinant vaccine production — e.g., Hepatitis B vaccine (recombinant HBsAg expressed in yeast).
- Recombinant therapeutic protein production — e.g., recombinant human insulin, growth hormone, clotting factors, interferons.
- Monoclonal antibody/biologic drug production — engineered cell lines producing therapeutic antibodies.
- Gene therapy — introducing a functional gene copy to treat single-gene disorders (e.g., SCID).
- Diagnostic applications — PCR-based molecular diagnostics, gene probes.
- Agricultural biotechnology — genetically modified crops with improved yield/pest resistance (outside the immediate medical sphere but a major application area).
- Production of diagnostic reagents — recombinant antigens for serological test kits.
Significance: genetic engineering has revolutionized vaccine production (safer, since no live/whole pathogen is needed), enabled mass production of previously scarce therapeutic proteins (e.g., insulin, previously extracted from animal pancreas), and underlies modern precision/molecular medicine.