Question

Why is it essential to have ‘selectable marker’ in a cloning vector ?

Hint:

The genes encoding resistance to antibiotics like ampicillin, chloramphenicol, tetracycline, or kanamycin are considered useful selectable markers for {E. coli}.

Answer 1

Step 1: Understanding the Concept:
After a transformation experiment, only a very small percentage of bacterial cells actually take up the foreign DNA. Scientists need a way to find those specific cells.
Step 2: Detailed Explanation:
1. Identification: A selectable marker is a gene (usually an antibiotic resistance gene like ampR or tetR) that allows researchers to distinguish between cells that have taken up the vector and those that have not.
2. Selection: Non-transformed cells will die in the presence of the selective agent (antibiotic), while transformed cells will survive and multiply.
3. Efficiency: Without a selectable marker, it would be impossible to isolate the few successful recombinant cells from millions of unsuccessful ones.
Step 3: Final Answer:
Selectable markers are vital for the selective growth of transformed host cells and for eliminating non-transformed cells during the screening process.