Why do we believe chloroplasts and mitochondria to be semi-autonomous organelle ?

Explanation

### Step-by-Step Solution

1. **Definition of Semi-Autonomous Organelles**: Chloroplasts and mitochondria are referred to as semi-autonomous organelles because they possess some characteristics that allow them to function independently within the cell.

2. **Presence of Extra Chromosomal DNA**: Both chloroplasts and mitochondria contain their own DNA, which is separate from the nuclear DNA of the cell. This extra chromosomal DNA is essential for their function and replication.

3. **70S Ribosomes**: These organelles have 70S ribosomes, which are similar to those found in prokaryotic cells. This allows them to synthesize some of their own proteins independently of the cell's nuclear DNA.

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