Select the incorrect statement from the following .

Options

A. Cistron is segment of DNA coding for a polypeptide.
B. The coding sequence or expressed sequences are defined as exons
C. Introns or intervening sequences appears in mature or processed RNA
D. Split gene arrangement is present in eukaryotes.

Answer

To solve the question of selecting the incorrect statement from the provided options, we need to analyze each statement carefully.

### Step-by-Step Solution:

1. **Understanding Cistron**:
- **Statement 1**: "Cistron is a segment of DNA coding for a polypeptide."
- **Analysis**: This statement is correct. A cistron refers to a segment of DNA that encodes for a specific polypeptide chain.

**Hint**: Remember that a cistron is synonymous with a gene that codes for proteins.

2. **Understanding Exons and Introns**:
- **Statement 2**: "The coding sequence or the expressed sequence are called as exons."
- **Analysis**: This statement is also correct. Exons are the parts of a gene that are expressed and retained in the final mRNA after splicing.

**Hint**: Exons are the coding regions, while introns are the non-coding regions that are removed during RNA processing.

3. **Understanding Introns**:
- **Statement 3**: "Introns are intervening segments; they appear in the mature or processed RNA."
- **Analysis**: This statement is incorrect. Introns are removed during RNA splicing and do not appear in the mature or processed RNA.

**Hint**: Focus on the process of splicing, which removes introns from the pre-mRNA.

4. **Understanding Split Genes**:
- **Statement 4**: "The split gene arrangement is present in eukaryotes."
- **Analysis**: This statement is correct. Eukaryotic genes often contain both exons and introns, leading to a split gene arrangement.

**Hint**: Split genes are a characteristic feature of eukaryotic organisms, distinguishing them from prokaryotes.

### Conclusion:
After analyzing all the statements, we find that Statement 3 is the incorrect one. Therefore, the answer to the question is that the incorrect statement is:

**Answer**: Statement 3: "Introns are intervening segments; they appear in the mature or processed RNA."