Biotechnology and Its Applications
Biotechnology and Its Applications tests recombinant DNA tools, PCR, gel electrophoresis, transgenic organisms, gene therapy and biosafety.
Core rules
- Restriction endonucleases cut DNA at specific sequences and often create sticky ends; DNA ligase joins fragments.
- A vector needs an origin of replication, selectable marker and recognition sites; transformation introduces recombinant DNA into a host.
- PCR has denaturation near 94-96 C, annealing near 50-65 C and extension near 72 C with Taq polymerase.
- Gel electrophoresis moves negatively charged DNA toward the anode; smaller fragments move farther.
- Human insulin is produced using A and B chain genes; Bt toxin gene comes from Bacillus thuringiensis; ADA gene therapy treats ADA deficiency.
Worked example
Starting with one DNA molecule, 30 PCR cycles produce 2^30 copies, about 1.07 billion copies. The reasoning is exponential amplification: each cycle doubles the target. After 10 cycles there are 2^10 = 1,024 copies; after 20 cycles, about one million; after 30 cycles, about one billion. This explains why PCR can detect trace DNA.
Traps
- DNA migrates toward the positive electrode, not the negative one.
- Taq polymerase is thermostable; ordinary DNA polymerase denatures at PCR temperatures.
- Restriction enzymes cut; ligase joins.
- Bt toxin is activated in the alkaline insect gut, not in the plant itself.