Which of the following is correct about mature RNA in eukaryotes?

Options

A. Exons and introns do not appear in the mature RNA
B. Exons appear, but introns do not appear in the mature RNA
C. Introns appear, but exons do not appear in the mature RNA
D. Both exons and introns appear in the mature RNA

Explanation

To answer the question "Which of the following is correct about mature RNA in eukaryotes?", we need to understand the process of RNA maturation in eukaryotic cells. Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understanding Transcription**:
- In eukaryotes, the process of transcription occurs in the nucleus where DNA is transcribed into pre-mRNA (precursor mRNA).
- This pre-mRNA contains both coding regions (exons) and non-coding regions (introns).

**Hint**: Remember that transcription produces a precursor form of RNA that includes both exons and introns.

2. **Pre-mRNA Composition**:
- The pre-mRNA consists of sequences that will eventually be processed to form mature RNA.
- Exons are the segments that code for proteins, while introns are non-coding segments that need to be removed.

**Hint**: Identify the roles of exons and introns in the pre-mRNA structure.

3. **RNA Processing**:
- After transcription, the pre-mRNA undergoes several modifications, including splicing, capping, and polyadenylation.
- During splicing, introns are removed, and exons are joined together to form a continuous coding sequence.

**Hint**: Focus on the splicing process, which is crucial for the maturation of RNA.

4. **Formation of Mature RNA**:
- The result of this processing is mature RNA, which is now ready for translation.
- Importantly, mature RNA in eukaryotes contains only exons, as introns have been removed during splicing.

**Hint**: Mature RNA is defined by the absence of introns and the presence of exons.

5. **Conclusion**:
- Based on the above understanding, the correct statement about mature RNA in eukaryotes is: "Exons appear, but introns do not appear in mature RNA."

**Final Answer**: The correct option is "Exons appear, but introns do not appear in mature RNA."