Control of gene experssion takes place at the level of

Options

A. DNA-replication
B. transcription
C. translation
D. None of these

Explanation

**Step-by-Step Solution:**

1. **Understanding Gene Expression**: Gene expression refers to the process by which information from a gene is used to synthesize a functional gene product, typically proteins. The regulation of this process is crucial for cellular function and differentiation.

2. **Identifying Levels of Control**: Gene expression can be controlled at multiple levels:
- **Transcription Level**: This is the first step where the DNA is transcribed into mRNA. Regulation at this level determines how much mRNA is produced from a gene.
- **Processing Level**: In eukaryotes, after transcription, the primary mRNA transcript undergoes processing, which includes splicing, capping, and polyadenylation.
- **Transport Level**: The processed mRNA is transported from the nucleus to the cytoplasm, where it can be translated into protein.
- **Translation Level**: This is where the mRNA is translated into a polypeptide chain, which will fold into a functional protein.

3. **Eukaryotic vs. Prokaryotic Control**:
- In **eukaryotes**, gene expression is regulated at multiple levels, with transcription being a primary control point.
- In **prokaryotes**, the control of gene expression primarily occurs at the transcriptional initiation level, which is the beginning of the transcription process.

4. **Conclusion**: Given the options provided (DNA replication, transcription, translation, none of these), the most significant level of control for gene expression is at the transcription level.

5. **Final Answer**: The control of gene expression takes place primarily at the level of **transcription**.

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