Question

pBluescriptSK is an example of

• A. Phagemid vector
• B. Cosmid vector
• C. Phasmid vector
• D. Plasmid vector

Hint:

A Phagemid = Plasmid origin + Phage (f1/M13) origin. This hybrid structure allows researchers to easily switch between double-stranded plasmid propagation and single-stranded DNA production.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Cloning vectors are vehicle DNA molecules used to carry foreign genetic material into a host cell for replication or expression.
Different classes of vectors are engineered with specific replication origins and functional elements depending on the host and application.

Step 2: Detailed Explanation:
Let us analyze the structure of the pBluescriptSK vector:
- pBluescriptSK is a highly popular, commercially developed phagemid vector.
- A phagemid is a hybrid cloning vector constructed by combining key features of plasmids and bacteriophages.
- It contains a standard plasmid origin of replication (colE1) for double-stranded replication and maintenance within bacterial hosts.
- Additionally, it contains an origin of replication derived from a filamentous bacteriophage (f1 phage).
- When a host cell harboring pBluescriptSK is co-infected with a helper phage (like M13), the f1 origin is activated.
- This triggers single-stranded replication, packaging, and secretion of the vector DNA as single-stranded filamentous particles, which are highly useful for DNA sequencing and site-directed mutagenesis.
Therefore, pBluescriptSK is classified as a phagemid vector.

Step 3: Final Answer:
pBluescriptSK is an example of a Phagemid vector.