QUESTION: Which of the following is not a cloning vector?
A Cosmid
B PBR 322
C Sall
D Phagemid
ANSWER: Sall
| Vector | Nature | Description | Role in Cloning Process |
| Cosmid | Cloning vector | · Cosmids are hybrid vectors that combine the features of plasmids and bacteriophages. · They can carry larger DNA inserts compared to traditional plasmids. Cosmids contain an origin of replication for E. coli and a phage DNA packaging signal (cos site). These features allow cosmids to be packaged into phage particles and propagated in E. coli. | · Cosmids are utilized for cloning larger DNA fragments that might not fit into regular plasmids, enabling the study of larger genetic elements or entire genes. · They are especially useful for genomic libraries and mapping studies. |
| pBR322 | Cloning vector | · PBR322 is a small, circular DNA plasmid that was one of the earliest widely used cloning vectors. · It carries genes for antibiotic resistance (ampicillin and tetracycline) and a multiple cloning site (MCS). · The MCS contains multiple unique restriction sites for inserting DNA fragments. | · PBR322 is employed for cloning small to moderate-sized DNA fragments. · It is a versatile vector suitable for general cloning, DNA sequencing and protein expression. · Its antibiotic resistance markers aid in selection and maintenance of transformed bacteria. |
| Phagemid | Cloning vector | · Phagemids are hybrid vectors combining features of both plasmids and filamentous bacteriophages. · They have an origin of replication for E. coli and a phage origin of replication. · Phagemids can replicate as plasmids within bacterial cells or produce phage particles that encapsulate single-stranded DNA. | · Phagemids are used for cloning and expression of DNA sequences. · They can be easily propagated as plasmids or as phage particles, allowing for the production of single-stranded DNA for sequencing or for generating DNA libraries. |
| Sall
| Enzyme
| · Sall is a type II restriction enzyme that recognizes the DNA sequence 5′-GTCGAC-3′. · It cleaves the DNA at this specific site.
| · Sall is not a cloning vector but rather an enzyme used in the digestion of DNA during cloning procedures. · It helps to generate compatible ends for ligation when inserting DNA fragments into vectors that have been linearized with the same enzyme. |