Home › Biology Class 12 › Biotechnology and its Applications
Biotechnology and its Applications
Biology · Class 12NCERT pp. 177–1852 sets × 25 questions
Key facts and formulas for Biotechnology and its Applications, three worked sample questions, and two full practice sets. Every question has a hint, a reason for every option and a step-by-step solution, with a calculator or animation where one helps. English and Hinglish.
Key facts for this chapter
| Idea | Rule or fact |
|---|
| Micro-propagation | Plant tissue culture gives identical plants (somaclones); meristem culture gives virus-free plants |
| Culture medium | Auxins and cytokinins; high cytokinin:auxin gives shoots, high auxin:cytokinin gives roots |
| Bt toxin | Inactive protoxin in the bacterium; activated by alkaline gut pH; makes pores in midgut cells |
| cry genes | cryIAc and cryIIAb for cotton bollworm; cryIAb for corn borer |
| RNAi | dsRNA is cut by Dicer into siRNA, silencing the matching mRNA; used against root-knot nematode in tobacco |
| Insulin | Mature insulin: chain A (21 aa) + chain B (30 aa) = 51 aa; pro-insulin has the C peptide |
| Diagnosis | PCR amplifies nucleic acid; ELISA uses antigen-antibody reaction; probe hybridisation shows only normal sequences |
| Gene therapy | First case in 1990 for ADA deficiency (SCID); ADA gene is deleted |
| Transgenic animals | Disease models, vaccine safety, biological products (alpha-1-antitrypsin), Rosie's milk with alpha-lactalbumin |
| Ethics and law | GEAC checks GM safety; biopiracy is unauthorised use of bio-resources; Basmati patent by US office; Biological Diversity Act 2002 |
Three sample questions
Q1. Assertion (A): Culturing the meristem of a virus-infected plant gives virus-free plants.
Reason (R): The apical and axillary meristems of an infected plant remain free of the virus.
- Both A and R are true but R is not the correct explanation of A
- Both A and R are true and R is the correct explanation of A
- A is true but R is false
- A is false but R is true
Hint and solution
Hint: Ask whether the reason explains why the assertion works. Why would cells from the growing tip give clean plants?
- A: meristem culture → virus-free plants — Check the assertion first. Meristem culture of infected plants is used to get virus-free plants, so A is true.
- R: apical and axillary meristems = virus-free — NCERT says the meristems of an infected plant are free of virus. So R is also true.
- Does R explain A? — The clean plants arise from clean cells. R is the exact reason A works.
- Both true, R explains A — So both are true and R is the correct explanation. Option B.
Answer: B. The meristems stay virus-free, so plants grown from them in vitro carry no virus. Done for banana, sugarcane and potato.
Q2. Consider these statements.
I. Plants raised by micro-propagation are somaclones.
II. Somatic hybrids arise from fused protoplasts of two varieties.
III. The pomato is a somaclone of tomato.
Which are correct?
- II and III only
- I and III only
- I, II and III
- I and II only
Hint and solution
Hint: A somaclone is a copy of one parent. Think about what the pomato was made from.
- Somaclone = identical copy of one parent — Plants from micro-propagation are genetically identical to the parent, so I is true.
- Somatic hybrid = fused protoplasts — Fusing protoplasts of two varieties or species gives a somatic hybrid, so II is true.
- Pomato = tomato + potato — The pomato is a somatic hybrid and not a copy of tomato, so III is false.
- Correct: I and II only — Only I and II are correct. Option D.
Answer: D. Somaclones are identical copies from one parent. A somatic hybrid (like the pomato) comes from fusing protoplasts of two plants, so III is wrong.
Q3. Which pair of growth regulators is added to the nutrient medium in plant tissue culture?
- Auxins and cytokinins
- Insulin and glucagon
- Ethylene and ABA only
- Antibodies and antigens
Hint and solution
Hint: Think of plant hormones that control root and shoot formation.
- Medium = sucrose + salts + vitamins + hormones — The nutrient medium carries a carbon source, inorganic salts, amino acids, vitamins and growth regulators.
- Plant growth regulators = auxins, cytokinins — These two hormones control cell division and the formation of roots and shoots.
- Eliminate animal and immune terms — Insulin, glucagon, antibodies and antigens are not plant growth regulators.
- Answer: auxins and cytokinins — So the pair is auxins and cytokinins. Option A.
Answer: A. The medium has sucrose, inorganic salts, amino acids, vitamins and growth regulators such as auxins and cytokinins.
How to use this chapter
Read the NCERT pages first, then attempt Set 1 without the hints. Note every wrong answer in a mistake list, read the reason for each option, and retry Set 2 two days later. A topic is solid when you can say why each wrong option is wrong.