Biotechnology – DNB CET Study Notes
Target exam: DNB CET (Biology)
Exam style: IIT‑JEE/competitive – emphasis on conceptual depth, derivations, formulae, tricky points, and application problems.
1. What is Biotechnology?
| Definition | Key Idea | Scope |
|---|---|---|
| Biotechnology = the application of living organisms or their components to produce useful products or processes. | Living system → engineered → product | Medical, food, agriculture, industrial, environmental |
Historical milestones
| Year | Event |
|---|---|
| 1973 | First recombinant DNA experiment (Sambrook et al.) |
| 1978 | First GM crop (MON‑810 maize) |
| 1990 | First recombinant protein drug (Humira) |
| 2003 | First genome‑edited animal (CRISPR‑edited mouse) |
| 2013 | First CRISPR‑edited human embryos (Kang et al.) |
| 2023 | FDA approval of first CRISPR‑based therapeutic (CTX001) |
2. Classification of Biotechnology
| Type | Primary Tool | Representative Application |
|---|---|---|
| Traditional | Selection, breeding | Hybrid crops |
| Modern (Molecular) | Recombinant DNA, cloning, PCR | GM crops, GM animals |
| Advanced (Genomic & Synthetic) | CRISPR, TALEN, ZFN, synthetic biology | Gene therapy, de‑novo genomes |
Key takeaway: Modern and Advanced technologies are the focus of competitive exams.
3. Core Molecular Techniques
3.1 Gene Cloning & Recombinant DNA
- Restriction digestion → blunt/compatible ends
- Ligation (T4 DNA ligase) → plasmid vector + insert
- Transformation (chemical/heat shock, electroporation) into E. coli
- Selection (antibiotic, blue‑white screening)
- Screening (PCR, colony‑lift, sequencing)
Tricky point: Distinguish cloning (insert into vector) vs. expression (production of protein in host).
3.2 Polymerase Chain Reaction (PCR)
| Step | Time | Temperature | Key Point |
|---|---|---|---|
| Denaturation | 30–60 s | 94–98 °C | DNA strands separate |
| Annealing | 30–60 s | (T_{m} - 3) °C (primer‑dependent) | Primer binds |
| Extension | 30–60 s | 72 °C | DNA polymerase (Taq) adds nucleotides |
3.2.1 Primer Melting Temperature (Tm)
[ T_m = 2^\circ\text{C},(A+T) + 4^\circ\text{C},(G+C) ] Use this simple rule for primers < 20 nt; for > 20 nt, use nearest‑neighbor thermodynamics.
3.2.2 PCR Product Yield
Assuming 100 % efficiency: [ N = N_0 \times 2^n ]
- (N_0) = initial copy number
- (n) = number of cycles
Tricky point: In practice, efficiency < 100 %; after ~30 cycles, plateau occurs.
3.3 Gel Electrophoresis
| Type | Principle | Key Feature |
|---|---|---|
| Agarose | Size‑based separation (SDS absent) | DNA fragments 200 bp–10 kb |
| SDS‑ |