Menthyl guanosine triphosphate is added to the 5' end of hnRNA in a process of

Options

A. splicing
B. capping
C. tailing
D. None of these

Explanation

To solve the question regarding the addition of methyl guanosine triphosphate to the 5' end of hnRNA, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding hnRNA**:
- Heterogeneous nuclear RNA (hnRNA) is the primary transcript that is synthesized from DNA during transcription. It includes both coding (exons) and non-coding (introns) sequences.

**Hint**: Remember that hnRNA is the precursor to mRNA and contains both exons and introns.

2. **Identifying the Modification**:
- The question mentions the addition of methyl guanosine triphosphate (m7GTP) to the 5' end of hnRNA. This modification is crucial for the stability and processing of the RNA.

**Hint**: Think about what modifications occur at the 5' end of RNA molecules.

3. **Recognizing the Process**:
- The addition of the methyl guanosine cap (m7G cap) is known as "capping". This process involves the conversion of GTP to 7-methyl guanosine and its attachment to the 5' end of the RNA.

**Hint**: This process is specifically referred to as "capping" and is essential for mRNA stability.

4. **Function of Capping**:
- The capping process serves multiple functions, including protecting the mRNA from degradation by nucleases, facilitating ribosome binding during translation, and aiding in the export of mRNA from the nucleus to the cytoplasm.

**Hint**: Consider why the capping of mRNA is important for its function in the cell.

5. **Differentiating from Other Processes**:
- It’s important to differentiate capping from other processes such as splicing (removal of introns) and tailing (addition of a poly-A tail at the 3' end).

**Hint**: Recall the definitions of splicing and tailing to clarify why they are not the correct answers.

6. **Conclusion**:
- Based on the above analysis, the correct answer to the question is that the addition of methyl guanosine triphosphate to the 5' end of hnRNA occurs in a process known as "capping".

**Final Answer**: The correct option is 2, capping.