With regard to mature mRNA in eukaryotes, which statement is correct?

Options

A. both exons and introns are absent
B. both exons and introns are present
C. exons present, introns absent
D. introns present, exons absent

Answer

To determine the correct statement regarding mature mRNA in eukaryotes, we will follow these steps:

### Step 1: Understand the Structure of mRNA
- Mature mRNA is produced from the initial transcript (immature mRNA) through a process called post-transcriptional modification.
- Immature mRNA contains both exons (coding sequences) and introns (non-coding sequences).

**Hint:** Remember that exons are the parts of the mRNA that will be translated into protein, while introns are removed during processing.

### Step 2: Identify the Post-Transcriptional Modifications
- During post-transcriptional modification, introns are removed from the immature mRNA, and the exons are spliced together.
- This results in mature mRNA, which consists only of exons.

**Hint:** Think about what happens to introns during the processing of mRNA. They are cut out!

### Step 3: Analyze the Statements
1. **Both exons and introns are absent.** - This is incorrect because mature mRNA contains exons.
2. **Both exons and introns are present.** - This is also incorrect since mature mRNA does not contain introns.
3. **Exons present, introns absent.** - This is correct as mature mRNA only contains exons after introns have been removed.
4. **Introns present, exons absent.** - This is incorrect because mature mRNA does not have introns.

**Hint:** Compare each statement with your understanding of what mature mRNA consists of after processing.

### Step 4: Conclusion
- The correct statement regarding mature mRNA in eukaryotes is that it contains exons and is devoid of introns.

**Final Answer:** The correct statement is: **Exons present, introns absent.**