UPSC Prelims 2014 Q72: Science & Technology – Biotechnology & Genetics
Consider the following techniques/phenomena :
1. Budding and grafting in fruit plants
2. Cytoplasmic male sterility
3. Gene silencing
Which of the above is/are used to create transgenic crops?
- (a) 1 only
- (b) 2 and 3
- (c) 1 and 3
- (d) None
Answer: (b) 2 and 3
Explanation
Techniques used to create transgenic crops
A transgenic crop carries a gene from another species, put in by genetic engineering.
| Technique | Used to create transgenic crops? | Fact |
|---|---|---|
| 1. Budding and grafting in fruit plants | No | Ordinary vegetative propagation; no gene is added |
| 2. Cytoplasmic male sterility | Yes | Engineered male sterility (for example the barnase-barstar system) is used to make hybrid seed, as in GM mustard |
| 3. Gene silencing | Yes | RNA interference switches off a chosen gene |
Examples:
| Crop | Technique |
|---|---|
| Bt cotton | Gene from the bacterium Bacillus thuringiensis |
| Flavr Savr tomato | Gene silencing to delay softening |
| GM mustard (DMH-11) | Male sterility genes for hybrid seed |
| Golden Rice | Genes for beta-carotene |
Answer: (b) 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Budding and grafting do not create transgenic crops.
- (b) CORRECT. Cytoplasmic male sterility and gene silencing are used in transgenic crops.
- (c) Incorrect. Budding and grafting add no foreign gene.
- (d) Incorrect. Two of the three are used, so 'None' is wrong.
Key point
Transgenic crops use genetic engineering: male sterility systems (GM mustard), gene silencing or RNAi (Flavr Savr), foreign genes (Bt cotton). Grafting is not genetic engineering.
Remember
Transgenic tools: male sterility genes, gene silencing.
Common mistakes
- Counting grafting as genetic modification.
- Not knowing that GM mustard rests on a male sterility system.
- Forgetting RNA interference as the tool of gene silencing.
Exam tip
Transgenic = a gene is put in or switched off in the laboratory. Farm techniques such as grafting do not count.
Sources
- NCERT Class XII — Biology (Biotechnology and its Applications)
- Genetic Engineering Appraisal Committee — Assessment of GM mustard DMH-11