Biotechnology: MDCAT Notes and MCQs
Recombinant DNA technology (genetic engineering) — key tools
- Restriction enzymes ("molecular scissors") cut DNA at specific sequences, often leaving sticky ends (e.g. EcoRI).
- DNA ligase ("molecular glue") joins DNA fragments.
- Vectors: plasmids (circular extra-chromosomal DNA of bacteria), viruses. Host often E. coli or yeast.
- PCR (Kary Mullis) amplifies DNA using heat-stable Taq polymerase.
Vaccines
- Traditional vaccines use killed/attenuated pathogens. Biotech makes subunit vaccines: a gene for a pathogen's surface antigen is inserted into bacteria/yeast, which produce only that protein — safe, no risk of infection.
- Example: hepatitis B vaccine (HBsAg made in yeast) — first recombinant vaccine. Also HPV vaccine, mRNA vaccines (COVID-19).
Diagnosis
- DNA/RNA probes: short, labelled (radioactive/fluorescent) single-stranded nucleic acid that binds a complementary sequence → detects pathogens and genetic disorders (e.g. sickle-cell, HIV, cystic fibrosis).
- Monoclonal antibodies (Köhler & Milstein, 1975): hybridoma = antibody-producing B-cell fused with a myeloma (cancer) cell → immortal clone making one specific antibody. Uses: pregnancy test kits (detect hCG), blood typing, cancer detection, targeted therapy.
- PCR-based tests, ELISA.
Treatment products
| Product | Use |
|---|---|
| Human insulin (Humulin, 1982 — first recombinant drug) | Diabetes mellitus |
| Human growth hormone (somatotropin) | Pituitary dwarfism |
| Interferons | Viral infections, some cancers |
| Tissue plasminogen activator (tPA) | Dissolves blood clots (heart attack, stroke) |
| Factor VIII | Haemophilia A |
| Erythropoietin, interleukins, antibiotics | Anaemia, immune therapy, infections |
Gene therapy: inserting a normal gene into a patient's cells (first trial 1990, ADA-SCID).
PMDC learning outcomes for this unit
- Biotechnology and Health Care: 16.1 Describe how biotechnologists can combat health problems by producing vaccines.
- Biotechnology and Health Care: 16.2 State the role played by biotechnology in disease diagnosis (DNA/RNA probes, monoclonal antibodies).
- Biotechnology and Health Care: 16.3 Describe what products biotechnologists obtain for use in disease treatment.