Question

Which of the following is not a desirable feature of a cloning vector?

• A. Presence of origin of replication
• B. Presence of a marker gene
• C. Presence of single restriction enzyme site
• D. Presence of two or more recognition sites

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
A cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted for cloning purposes. It must have certain features to be useful in biotechnology.
Detailed Explanation:
- (1) Origin of replication (ori): Essential for the vector to replicate inside the host cell.
- (2) Selectable marker: Essential to identify and select transformants from non-transformants (e.g., antibiotic resistance genes).
- (3) Single restriction site: Desirable for a specific enzyme so that the vector is cut at only one place, allowing easy insertion of foreign DNA.
- (4) Two or more recognition sites: Undesirable. If there are multiple recognition sites for the same enzyme, the vector will be cut into several fragments, which complicates the gene cloning process and makes it difficult to re-ligate the vector correctly.
Step 2: Final Answer:
Multiple recognition sites for a single enzyme are a disadvantage in a vector.