UPSC Prelims 2011 Q5: Science & Technology – Biotechnology & Genetics
At present, scientists can determine the arrangement or relative positions of genes or DNA
sequences on a chromosome. How does this knowledge benefit us?
1. It is possible to know the pedigree of livestock.
2. It is possible to understand the causes of all human diseases.
3. It is possible to develop disease - resistant animal breeds.
Which of the statements given above is/are correct?
- (a) 1 and 2 only
- (b) 2 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (c) 1 and 3 only
Explanation
Benefit of mapping gene positions on a chromosome
Knowing where genes sit on a chromosome (gene mapping) is the basis of genomics and selective breeding.
| Statement | Verdict | Reason |
|---|---|---|
| 1. Possible to know the pedigree of livestock | Correct | DNA markers linked to known gene positions can trace parentage and lineage |
| 2. Possible to understand the causes of all human diseases | Incorrect | Gene mapping helps with genetic diseases, but most diseases are multi-factorial (environment, lifestyle, infections); 'all' is too strong |
| 3. Possible to develop disease-resistant animal breeds | Correct | Mapping lets breeders select for genes linked to disease resistance |
Applications of gene mapping:
| Use | Example |
|---|---|
| Livestock pedigree | DNA-based parentage verification |
| Breeding | Selecting disease-resistant or high-yield breeds |
| Medicine | Identifying genetic disease markers (not all diseases) |
Answer: (c) 1 and 3 only.
Why each option is right or wrong
- (a) Incorrect. Statement 2 overreaches; gene mapping cannot explain all human diseases, and statement 3 is left out.
- (b) Incorrect. Statement 1 is also true, and statement 2's 'all diseases' claim is too strong.
- (c) CORRECT. Livestock pedigree tracing and breeding disease-resistant animals are real benefits.
- (d) Incorrect. Statement 2's claim to explain all human diseases is an overreach.
Key point
Gene mapping benefits: livestock pedigree tracing, breeding disease-resistant animals. It does NOT explain 'all' human diseases, most of which are multi-factorial.
Remember
Gene mapping: pedigree + disease-resistant breeding, not 'all' disease causes.
Common mistakes
- Accepting absolute words like 'all' in a statement about disease causation.
- Underestimating the livestock breeding use of gene mapping.
- Forgetting that most diseases involve environment and lifestyle, not genes alone.
Exam tip
A statement claiming to explain 'all' of something complex (like disease) is almost always an overreach.
Sources
- NCERT Class XII — Biology, Ch 6 (Molecular Basis of Inheritance)
- National Human Genome Research Institute — Genetic Mapping Fact Sheet