IIT JAM Biotechnology: Molecular Mechanisms and Quantitative Biology
Biotechnology in IIT JAM BT tests undergraduate cell and molecular biology, biochemistry, genetics, microbiology, immunology, bioprocess principles and recombinant DNA methods. Questions reward mechanism-based reasoning and simple calculations, not descriptive recall alone.
Core rules and concepts
- Central dogma: replication is semiconservative; transcription uses the template strand 3′→5′ and makes RNA 5′→3′; translation reads mRNA codons 5′→3′.
- Enzyme kinetics: for Michaelis–Menten, v = Vmax[S]/(Km + [S]); Km is the substrate concentration at half Vmax. A competitive inhibitor raises apparent Km but leaves Vmax unchanged.
- Genetics: segregation and independent assortment; Hardy–Weinberg p² + 2pq + q² = 1 requires random mating, large population, no selection, migration or mutation.
- Microbial growth: lag, log, stationary and death phases; in exponential phase, μ = ln2/t_d.
- Recombinant DNA: restriction digestion, ligation, transformation and selection; insert orientation and reading frame matter.
- Immunity: antibody–antigen specificity; the secondary response is faster and larger because of memory cells.
Worked example
A double-stranded DNA sample contains 30% adenine. Find the percentage of guanine. In dsDNA, A = T and G = C. If A = 30%, then T = 30%, so A + T = 60%. The remaining 40% is G + C, and because G = C, guanine is 20%.
Traps that cost marks
Do not apply Chargaff’s rules to single-stranded RNA. Do not confuse Km with Vmax. Do not treat stationary phase as growth. In restriction maps, check whether the insert is oriented correctly relative to the promoter.
Key points
- A = T and G = C only in double-stranded DNA.
- Km measures substrate affinity inversely, not reaction speed.
- Competitive inhibition changes apparent Km, not Vmax.
- Log-phase growth is exponential, with μ = ln2/t_d.
- Recombinant selection depends on vector markers and insert orientation.