UPSC Prelims 2019 Q93: Science & Technology – Biotechnology & Genetics
With reference to the recent developments in science,
which one of the following statements is not correct?
- (a) Functional chromosomes can be created by joining segments of DNA taken from cells of different species.
- (b) Pieces of artificial functional DNA can be created in laboratories.
- (c) A piece of DNA taken out from an animal cell can be made to replicate outside a living cell in a laboratory.
- (d) Cells taken out from plants and animals can be made to undergo cell division in laboratory petri dishes.
Answer: (a) Functional chromosomes can be created by joining segments of DNA taken from cells of different species.
Explanation
Recent developments in science: which statement is not correct?
| Option | True? | Basis |
|---|---|---|
| (a) Functional chromosomes can be created by joining segments of DNA taken from cells of different species | Not correct (the answer) | Joining DNA of different species gives recombinant DNA carrying a few genes; a whole working chromosome had not been made this way |
| (b) Pieces of artificial functional DNA can be created in laboratories | Correct | Synthetic DNA is made routinely; a synthetic bacterial genome was built in 2010 |
| (c) A piece of DNA taken out from an animal cell can be made to replicate outside a living cell in a laboratory | Correct | The polymerase chain reaction (PCR) copies DNA in a test tube |
| (d) Cells taken out from plants and animals can be made to undergo cell division in laboratory petri dishes | Correct | Tissue culture and cell culture |
Techniques to know:
| Technique | What it does |
|---|---|
| Recombinant DNA technology | Joins a gene from one species into the DNA of another (for example, human insulin made by bacteria) |
| PCR | Makes millions of copies of a DNA piece outside a cell |
| Tissue culture | Grows whole plants or cell lines from a few cells |
Answer: (a) Functional chromosomes can be created by joining segments of DNA taken from cells of different species.
Why each option is right or wrong
- (a) CORRECT. This is the statement that is not correct; a functional chromosome was not made by joining DNA of different species.
- (b) Incorrect. This statement is true; artificial functional DNA is made in laboratories.
- (c) Incorrect. This statement is true; PCR replicates DNA outside a living cell.
- (d) Incorrect. This statement is true; cells divide in petri dishes in tissue culture.
Key point
Recombinant DNA: genes joined across species. PCR: DNA copied outside cells. Tissue culture: cells divide in the laboratory. Synthetic DNA: made in laboratories.
Remember
PCR copies DNA outside the cell; tissue culture grows cells in a dish.
Common mistakes
- Forgetting that the question asks for the statement that is not correct.
- Reading 'DNA segments' in option (a) and missing the bigger claim of a whole functional chromosome.
- Doubting option (c) because DNA normally replicates only inside cells; PCR does it outside.
Exam tip
In 'not correct' questions, look for the option that claims the most. A whole functional chromosome is a far bigger claim than a piece of DNA.
Sources
- NCERT Class XII — Biology, Ch 11 (Biotechnology: Principles and Processes)
- J. Craig Venter Institute — First self-replicating synthetic bacterial cell (2010)