CAPF AC 2023 Q19: Science & Technology – Biology
- (a) Golgi
- (b) Mitochondria
- (c) Lysosomes
- (d) Nucleosomes
Answer: (b) Mitochondria
Explanation
Organelles with their own DNA
How to think: two organelles are called semi-autonomous because they have their own DNA and ribosomes and can make some of their own proteins.
They are mitochondria and, in plants, chloroplasts.
| Organelle | Own DNA? | Own ribosomes? | Function |
|---|---|---|---|
| Mitochondria | Yes, circular | Yes, 70S | Respiration; powerhouse of the cell |
| Chloroplast (plants) | Yes | Yes | Photosynthesis |
| Golgi apparatus | No | No | Packaging and secretion |
| Lysosome | No | No | Digestion; suicide bag |
A nucleosome is not an organelle.
It is a bead of DNA wound round histone proteins inside the nucleus.
Extra fact: mitochondrial DNA is inherited only from the mother.
Answer: (b) Mitochondria.
Why each option is right or wrong
- (a) Incorrect. The Golgi apparatus has no DNA or ribosomes of its own.
- (b) CORRECT. Mitochondria have their own DNA, ribosomes and proteins.
- (c) Incorrect. Lysosomes only store digestive enzymes.
- (d) Incorrect. Nucleosomes are units of chromatin, not organelles.
Key point
Semi-autonomous organelles: mitochondria and chloroplasts (own circular DNA, 70S ribosomes, double membrane). This supports the endosymbiotic theory. Mitochondrial DNA passes down the maternal line.
Remember
Mitochondria: own DNA and ribosomes.
Common mistakes
- Confusing nucleosome with nucleolus or with an organelle.
- Forgetting that mitochondria make some of their own proteins.
- Thinking only the nucleus contains DNA in an animal cell.
Exam tip
Educated guess: NCERT Class IX says it directly: mitochondria are strange organelles in the sense that they have their own DNA and ribosomes.
Sources
- NCERT Class IX Science — The Fundamental Unit of Life (mitochondria)
- NCERT Class XI Biology — Cell: The Unit of Life