A Levels Biology (9700)•9700/12/M/J/22
Explanation
Endosymbiotic features in organelles
Steps:
- Chloroplasts and mitochondria originated from ancient prokaryotic bacteria via endosymbiosis.
- Prokaryotes contain 70S ribosomes for protein synthesis and circular DNA as their genome.
- These organelles retain prokaryotic traits, unlike the eukaryotic cell's 80S ribosomes and linear DNA.
- Compare options to identify the matching prokaryotic features.
Why B is correct:
- Endosymbiotic theory defines these organelles by prokaryotic inheritance, including 70S ribosomes for translation and circular DNA for independent replication.
Why the others are wrong:
- A: Omits circular DNA, a key prokaryotic feature in both organelles.
- C: 80S ribosomes are eukaryotic cytoplasmic, not found in chloroplasts or mitochondria.
- D: Excludes 70S ribosomes, essential for organelle-specific protein synthesis.
Final answer: B
Topic: Cells as the basic units of living organisms
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