Which of the following reunites the exon segments after RNA splicing ?

Options

A. RNA polymerase
B. RNA primase
C. RNA ligase
D. RNA protease

Explanation

To solve the question "Which of the following reunites the exon segments after RNA splicing?", we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding HnRNA**:
- After transcription, the RNA produced is known as heterogeneous nuclear RNA (HnRNA). This RNA contains both exons (coding regions) and introns (non-coding regions).

2. **Identifying Exons and Introns**:
- In HnRNA, exons are the segments that code for proteins, while introns are the segments that do not code for proteins. For example, a sequence might look like this: E1 (exon) - I1 (intron) - E2 (exon) - I2 (intron) - E3 (exon).

3. **Process of Splicing**:
- To produce a mature mRNA that can be translated into a protein, the introns must be removed from the HnRNA. This process is known as splicing.

4. **Result of Splicing**:
- After splicing, the RNA will consist solely of the exons. For example, it will appear as E1 - E2 - E3, without any introns.

5. **Reuniting Exons**:
- The exons that remain after splicing need to be joined together to form a continuous coding sequence. This is where the enzyme comes into play.

6. **Role of RNA Ligase**:
- The enzyme responsible for joining the exon segments after RNA splicing is called RNA ligase. RNA ligase facilitates the formation of phosphodiester bonds between the exons, effectively reuniting them into a single, continuous strand of mRNA.

### Final Answer:
The enzyme that reunites the exon segments after RNA splicing is **RNA ligase**.

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