The vector requires a…………, which helps in identifying selectively permitting the growth of transformants.

Options

A. selectable marker
B. cloning sites
C. antibiotic resistance gene
D. bacteriophage

Answer

To solve the question regarding what a vector requires to selectively permit the growth of transformants, we can break down the information provided in the video transcript into clear steps.

### Step-by-Step Solution:

1. **Understanding the Role of Vectors**: Vectors are DNA molecules used to deliver genetic material into cells. They are essential tools in genetic engineering and molecular biology.

2. **Identifying Key Features of Vectors**:
- Vectors must have specific features to function effectively. Among these features, the most critical is the presence of a selectable marker.

3. **Defining Selectable Markers**:
- A selectable marker is a gene that allows for the identification of cells that have successfully taken up the vector containing the desired DNA. This is crucial for distinguishing between transformants (cells that have taken up the vector) and non-transformants (cells that have not).

4. **Mechanism of Selectable Markers**:
- Selectable markers often encode for antibiotic resistance. For instance, if a vector contains a gene for ampicillin resistance, only those cells that have been transformed with the vector will survive in a medium containing ampicillin. Non-transformants will not survive because they lack this resistance gene.

5. **Conclusion**:
- Therefore, the vector requires a **selectable marker** that helps in identifying and selectively permitting the growth of transformants.

### Final Answer:
The vector requires a **selectable marker**, which helps in identifying selectively permitting the growth of transformants.