This RNA undergoes additional processing called as capping and tailing

Options

A. sn RNA
B. 5 sr RNA
C. m RNA
D. hn RNA

Answer

To answer the question regarding which RNA undergoes additional processing called capping and tailing, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Type of RNA**:
- The question asks about RNA that undergoes capping and tailing. The RNA synthesized by RNA polymerase II is known as heterogeneous nuclear RNA (hnRNA), also referred to as the primary transcript.

2. **Understand the Role of hnRNA**:
- hnRNA contains both introns (non-coding sequences) and exons (coding sequences). Before it can be translated into a protein, it must be processed to remove introns and prepare it for translation.

3. **Define Capping**:
- Capping is the addition of a special nucleotide, specifically 7-methylguanylate (m7G), to the 5' end of the hnRNA. This cap protects the RNA from degradation and assists in ribosome binding during translation.

4. **Define Tailing**:
- Tailing refers to the addition of a poly-A tail, which consists of 200 to 300 adenine nucleotides added to the 3' end of the hnRNA. This process is catalyzed by the enzyme poly(A) polymerase and also serves to protect the RNA from degradation.

5. **Splicing Process**:
- In addition to capping and tailing, hnRNA undergoes splicing, where introns are removed and exons are joined together. This results in a mature mRNA molecule that is ready for translation.

6. **Conclusion**:
- Therefore, the RNA that undergoes capping and tailing is hnRNA, which is converted into functional mRNA through these processing steps.

### Final Answer:
The RNA that undergoes additional processing called capping and tailing is **heterogeneous nuclear RNA (hnRNA)**.

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