Several proteins may be produced at the same time from a single m-RNA by :-

Options

A. the action of several ribosomes in a string called a polyribosome
B. several RNA polymerase molecules working sequentially
C. single peptides that associate ribosomes with rough E.R.
D. the involvement of multiple spliceosomes complex

Answer

To answer the question, "Several proteins may be produced at the same time from a single m-RNA by:", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding mRNA and Translation**:
- mRNA (messenger RNA) is a type of RNA that carries genetic information from DNA to the ribosome, where proteins are synthesized. The process of protein synthesis is called translation.

2. **Role of Ribosomes**:
- Ribosomes are the cellular machinery that translate mRNA into proteins. They read the sequence of the mRNA and assemble the corresponding amino acids to form proteins.

3. **Polyribosomes (Polysomes)**:
- Multiple ribosomes can attach to a single mRNA strand simultaneously. This structure is known as a polyribosome or polysome. Each ribosome translates the mRNA into a protein, allowing for the production of multiple copies of a protein from a single mRNA molecule.

4. **Evaluating the Options**:
- **Option 1**: The action of several ribosomes in a string called polyribosome. This is correct as it describes how multiple proteins can be synthesized from one mRNA.
- **Option 2**: Several RNA polymerase molecules working sequentially. This is incorrect because RNA polymerase is involved in transcription, not translation.
- **Option 3**: Single peptides that associate ribosomes with rough ER. This is incorrect as it does not pertain to the simultaneous production of proteins from a single mRNA.
- **Option 4**: The involvement of multiple spliceosome complexes. This is incorrect because spliceosomes are involved in mRNA processing, not in the translation process.

5. **Conclusion**:
- The correct answer is **Option 1**: The action of several ribosomes in a string called polyribosome, as this allows for the simultaneous production of multiple proteins from a single mRNA strand.