In eukaryotes, hn RNA transforms into mRNA by

Options

A. 5. capping
B. Intron transcripts removal and exon transcripts joining
C. Polyadenylation at 3. end
D. All these steps

Answer

To solve the question regarding how hnRNA transforms into mRNA in eukaryotes, we can break down the process into clear steps:

### Step-by-Step Solution:

1. **Understanding hnRNA**:
- hnRNA (heterogeneous nuclear RNA) is the initial transcript synthesized from DNA in eukaryotic cells. It contains both introns (non-coding regions) and exons (coding regions).

2. **5' Capping**:
- The first step in the transformation of hnRNA to mRNA is the addition of a 5' cap. This cap is a modified guanine nucleotide that is added to the 5' end of the hnRNA. It protects the RNA from degradation and assists in ribosome binding during translation.

3. **Intron Removal and Exon Joining**:
- The second step involves the removal of introns through a process called splicing. The exons, which are the coding sequences, are then joined together. This process is crucial as it ensures that the final mRNA only contains the necessary coding information.

4. **Polyadenylation**:
- The final step is polyadenylation, where a poly(A) tail is added to the 3' end of the mRNA. This tail consists of a long sequence of adenine nucleotides, which also helps protect the mRNA from degradation and aids in the export of the mRNA from the nucleus to the cytoplasm.

5. **Conclusion**:
- After these three steps (5' capping, intron removal and exon joining, and polyadenylation), the hnRNA is fully processed into mature mRNA, ready for translation.

### Final Answer:
The transformation of hnRNA into mRNA in eukaryotes involves all these steps: 5' capping, intron removal and exon joining, and polyadenylation at the 3' end. Therefore, the correct answer is **option d: all these steps**.

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