Applied Biology and Biotechnology
Applied Biology and Biotechnology
This domain tests how biological knowledge is used in medicine, agriculture, and industry: genetic engineering, diagnostic techniques, fermentation, and reproductive technologies.
Core rules
- Recombinant DNA uses restriction enzymes to cut DNA, DNA ligase to join fragments, and vectors such as plasmids to carry genes into host cells.
- PCR amplifies DNA using denaturation, primer annealing, and extension by a heat-stable DNA polymerase such as Taq.
- Gel electrophoresis separates DNA fragments by size; smaller fragments move farther through the gel.
- CRISPR–Cas9 uses a guide RNA to target a specific DNA sequence and a Cas nuclease to cut it, enabling gene editing.
- Monoclonal antibodies are produced from a single B-cell clone fused with a myeloma cell, giving a uniform antibody.
- Industrial fermentation uses microorganisms in controlled conditions to produce antibiotics, enzymes, or fuels.
Worked example
A single DNA molecule is amplified by PCR for 20 cycles. Amplification is 2²⁰ ≈ 1.05 × 10⁶, so about one million copies are produced. Reasoning: each cycle doubles the number of target molecules, assuming near-100% efficiency. Thirty cycles would give over one billion copies.
Traps
- PCR detects DNA, not protein; ELISA or Western blotting is used for proteins.
- Primers must be complementary to sequences flanking the target region.
- Restriction enzymes cut at specific recognition sites; they are not the same as DNA ligase.
- In gel electrophoresis, DNA is negatively charged and moves toward the positive electrode.