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. |
