Select an incorrect statement for a eukaryotic genes

Options

A. Split-gene arrangement complicates the definition of a gene
B. Inheritance of a character is affected by regulatory sequences of a structural gene.
C. Sometime the regulatory sequences do not code for any RNA or protein.
D. The structural gene in a transcription unit could be said as monocistronic mostly in prokaryotes or polycistronic mostly in eukaryotes

Answer

To solve the question of selecting an incorrect statement regarding eukaryotic genes, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Understanding Split Genes**:
- The first statement mentions that "Split gene arrangement complicates the definition of a gene."
- In eukaryotes, genes are often split into exons (expressed regions) and introns (non-coding regions). This complexity does indeed make defining a gene more complicated.
- **Conclusion**: This statement is **correct**.

2. **Regulatory Sequences and Inheritance**:
- The second statement states, "Inheritance of a character is affected by regulatory sequence of a structural gene."
- Regulatory sequences such as promoters and operators play a crucial role in gene expression. If these sequences are altered, it can affect the inheritance of traits.
- **Conclusion**: This statement is **correct**.

3. **Regulatory Sequences Not Coding for RNA or Protein**:
- The third statement claims, "Sometimes, the regulatory sequences do not code for any RNA or protein."
- This is true; regulatory sequences like promoters and enhancers do not code for proteins or RNA but are essential for the regulation of gene expression.
- **Conclusion**: This statement is **correct**.

4. **Monocistronic and Polycistronic Genes**:
- The fourth statement says, "The structural gene in a transcription unit could be seen as monocistronic mostly in prokaryotes or polycistronic mostly in eukaryotes."
- This is incorrect. In reality, eukaryotic genes are primarily monocistronic (one gene per mRNA), while prokaryotic genes can be polycistronic (multiple genes per mRNA).
- **Conclusion**: This statement is **incorrect**.

### Final Answer:
The incorrect statement regarding eukaryotic genes is the **fourth statement**.

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