UPSC Prelims 2022 Q99: Science & Technology – Biotechnology & Genetics
Consider the following statements: DNA Barcoding can be a tool to:
1. Assess the age of a plant or animal.
2. Distinguish among species that look alike.
3. Identify undesirable animal or plant materials in processed foods.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 3 only
- (c) 1 and 2
- (d) 2 and 3
Answer: (d) 2 and 3
Explanation
What DNA barcoding can and cannot do
DNA barcoding reads a short, standard gene region to identify the species a sample comes from.
| Group | Barcode gene |
|---|---|
| Animals | COI (mitochondrial cytochrome c oxidase I) |
| Plants | rbcL and matK (chloroplast genes) |
Checking the statements:
| Statement | Verdict | Reason |
|---|---|---|
| 1. Assess the age of a plant or animal | Incorrect | The barcode sequence is the same throughout life, so it reveals species, not age |
| 2. Distinguish look-alike species | Correct | It separates cryptic species that look identical |
| 3. Spot undesirable materials in processed food | Correct | It detects adulteration and mislabelling, such as pork in beef or cheap fish sold as premium |
Answer: (d) 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Statement 1 is false; a DNA barcode does not change with age.
- (b) Incorrect. Statement 2 is also true; barcoding separates look-alike species.
- (c) Incorrect. Barcoding cannot tell age, so statement 1 fails.
- (d) CORRECT. Barcoding identifies species, so it separates look-alikes and detects food adulteration.
Key point
DNA barcoding identifies species using a standard gene (COI in animals; rbcL and matK in plants); it cannot estimate age.
Remember
DNA barcode tells species, not age.
Common mistakes
- Thinking DNA analysis can tell age; that needs methods like radiocarbon dating or growth rings.
- Not seeing the use of barcoding in food fraud detection.
- Confusing barcoding with full genome sequencing.
Exam tip
Barcode = species ID tag. Ask whether the task needs species identity; if so, barcoding helps.
Sources
- Consortium for the Barcode of Life — What is DNA barcoding
- Food Safety and Standards Authority of India — Food adulteration testing