Applied Biology and Biotechnology
Applied Biology and Biotechnology
This domain tests recombinant DNA technology, PCR, electrophoresis, tissue culture, fermentation and the uses and risks of biotechnology. Expect questions on tool enzymes, steps in a procedure, and interpreting results.
Core rules
- Restriction endonucleases cut DNA at specific recognition sequences, often producing sticky ends. DNA ligase joins fragments. A plasmid vector carries a gene into a host cell, which is selected using a marker.
- PCR uses denaturation, primer annealing and extension by Taq polymerase. Each cycle doubles the DNA, so n cycles give 2ⁿ copies from one starting molecule.
- Gel electrophoresis separates DNA by size. DNA is negatively charged and moves toward the positive electrode; smaller fragments travel farther.
- Tissue culture uses totipotent plant cells to produce clones. Fermentation by yeast produces ethanol and CO2; lactic acid bacteria produce lactic acid.
Worked example
One DNA molecule undergoes 10 PCR cycles. Number of copies = 2¹⁰ = 1024. Reasoning: each cycle doubles the number, so after 1 cycle there are 2, after 2 there are 4, and after 10 there are 1024. This exponential amplification is why PCR can detect trace DNA.
Traps
Restriction enzymes cut DNA; ligase joins it. PCR is not the same as cloning an organism. Antibiotics do not treat viral infections. In gel electrophoresis, the well is near the negative electrode. A plasmid is a vector, not the gene itself.