Extra nuclear genes are usually present in mitochondria and…………..

Explanation

**Step-by-Step Solution:**

1. **Understanding Extranuclear Genes**: Extranuclear genes are those genes that are not located in the nucleus of a cell. Instead, they are found in organelles outside the nucleus.

2. **Identifying Organelles with Extranuclear Genes**: The primary organelles known to contain extranuclear genes are mitochondria and plastids.

3. **Function of Extranuclear Genes**: The main function of these extranuclear genes is to facilitate protein synthesis. This is crucial for the organelles to perform their specific functions, such as energy production in mitochondria and photosynthesis in plastids.

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