Topic: Complete One-Page Summary for Last-Day Revision
A. Insulin (Numbers must be exact)
- A chain = 21 aa | B chain = 30 aa | Connected by disulfide bonds | C peptide removed
- Produced by Eli Lilly in 1983 using E. coli | Replaced allergenic porcine/bovine insulin
B. Gene Therapy
- Disease: ADA deficiency (SCID)
- Vector: retroviral | Target: lymphocytes | Not permanent (lymphocytes die)
- Permanent cure: bone marrow transplant | Interim: PEG-ADA injection
C. Molecular Diagnostics (PEA)
| Test | Detects | Key Use |
|---|---|---|
| PCR | DNA/RNA (1 copy) | Early HIV, prenatal diagnosis |
| ELISA | Ag or Ab | HIV, hepatitis B, pregnancy |
| Autoradiography | DNA/RNA on membrane | Southern/Northern blot |
D. Bt Crops (Most NEET-tested — memorize exactly)
| Crop | Cry Gene(s) | Target Pest | Pest Order |
|---|---|---|---|
| Bt cotton | cry1Ac + cry2Ab | Cotton bollworm (Helicoverpa) | Lepidoptera |
| Bt corn | cry1Ab | European corn borer (Ostrinia) | Lepidoptera |
Bt toxin mechanism: Inactive crystalline protoxin (inside bacterium) → ingested by larva → alkaline gut pH (~10) dissolves crystal → gut proteases activate toxin → binds midgut epithelial receptors → pore formation → cell swelling → lysis → insect death
E. RNAi
- dsRNA → DICER → siRNA (21-23 nt) → RISC (AGO2) → mRNA cleavage → gene silenced
- Tobacco vs. Meloidogyne incognita (nematode): sense + antisense RNA → dsRNA → nematode gene silenced
F. GM Crops
- Golden Rice: beta-carotene in endosperm → provitamin A → vitamin A deficiency prevention
- Flavr Savr tomato: first GM food (1994) → antisense PG → delayed ripening
G. Transgenic Animals
| Animal | Product | Use |
|---|---|---|
| Rosie (cow) | Human alpha-lactalbumin | Infant nutrition |
| Transgenic sheep | Alpha-1-antitrypsin | Emphysema |
| Transgenic mice | Cancer/Alzheimer models | Drug testing, vaccine safety |
H. Biosafety & Biopiracy
- GEAC = Genetic Engineering Approval Committee = approves GMO field trials and commercial release
- Biopiracy NTB: Neem (EPO revoked) | Turmeric (USPTO revoked, Sanskrit prior art) | Basmati (RiceTec claims narrowed)
- CBD (1992): sovereign rights over biological resources
- Nagoya Protocol: PIC + MAT required before accessing biological resources
I. NEET Traps — Never Get These Wrong
- Bt toxin activated by ALKALINE pH (NOT acidic)
- cry1Ab = corn (NOT cotton); cotton = cry1Ac + cry2Ab
- Rosie = lactalbumin (NOT antitrypsin); sheep = antitrypsin
- Gene therapy = NOT permanent; bone marrow = permanent
- PEG-ADA = enzyme replacement, NOT gene therapy
- Biopiracy = NTB (three cases, not two)