Biotechnology and Its Applications
Biotechnology and Its Applications covers principles and processes, genetic engineering, and applications. Questions focus on tools, steps, and the logic of how a product works.
Core rules
- Restriction enzymes cut DNA at specific palindromic sequences, often producing sticky ends. DNA ligase joins fragments. A vector needs an origin of replication, a selectable marker, and a cloning site.
- PCR has three steps: denaturation at about 94-96 C, annealing of primers at about 50-60 C, and extension by Taq polymerase at about 72 C.
- Gel electrophoresis separates DNA fragments by size; DNA is negatively charged and moves toward the anode.
- Applications include Bt cotton, RNA interference against Meloidogyne incognita, human insulin, gene therapy for ADA deficiency, and molecular diagnosis by PCR or ELISA.
Worked example
Bt cotton kills bollworm larvae but does not kill Bacillus thuringiensis itself. Explain. Reasoning: the cry gene makes an inactive protoxin stored as a crystal. In the insect midgut, alkaline pH and proteases convert it into active toxin. The toxin binds midgut epithelial receptors, forms pores, and lyses cells. Bacillus keeps the protoxin inactive; humans lack the alkaline gut and specific receptors.
Traps
Restriction enzymes cut DNA, not protein. DNA fragments move toward the positive electrode, not the negative one. Ti plasmid comes from Agrobacterium tumefaciens. RNAi silences nematode mRNA; it is not a protein toxin. Insulin is first made as proinsulin and the C peptide must be removed.