“A cloning vector is a small piece of DNA into which a foreign DNA can be inserted for cloning purposes.”
What is a Cloning Vector?
A vector is a DNA molecule that is used to carry a foreign DNA into the host cell. It has the ability to self replicate and integrate into the host cell. These vectors have helped in analysing the molecular structure of DNA.
Vectors can be a plasmid from the bacterium, a cell from the higher organism or DNA from a virus. The target DNA is inserted into the specific sites of the vector and ligated by DNA ligase. The vector is then transformed into the host cell for replication.
Read on to explore the features and functions of cloning vectors.
Also Read: Recombinant DNA Technology
Features of Cloning Vectors
The cloning vectors possess the following features:
- A cloning vector should possess an origin of replication so that it can self-replicate inside the host cell.
- It should have a restriction site for the insertion of the target DNA.
- It should have a selectable marker with an antibiotic resistance gene that facilitates screening of the recombinant organism.
- It should be small in size so that it can easily integrate into the host cell.
- It should be capable of inserting a large segment of DNA.
- It should possess multiple cloning sites.
- It should be capable of working under the prokaryotic and eukaryotic systems.
Types of Cloning Vectors
There are the following different types of cloning vectors:
- These were the first vectors used in gene cloning.
- These are found in bacteria, eukaryotes and archaea.
- These are natural, extrachromosomal, self-replicating DNA molecules.
- They have a high copy number and possess antibiotic-resistant genes.
- They encode proteins which are necessary for their own replication.
- pBR322, pUC18, F-plasmid are some of the examples of plasmid vectors
- These are more efficient than plasmids for cloning large DNA inserts.
- Phage λ and M13 phage are commonly used bacteriophages in gene cloning.
- 53 kb DNA can be packaged in the bacteriophage.
- The screening of phage plaques is much easier than the screening of recombinant bacterial colonies.
- These are artificial vectors.
- They are used in combination with M13 phage.
- They possess multiple cloning sites and an inducible lac gene promoter.
- They are identified by blue-white screening.
Bacterial Artificial Chromosomes
- These are similar to E.coli plasmids vectors.
- It is obtained from naturally occurring F’ plasmid.
- These are used to study genetic disorders.
- They can accommodate large DNA sequences without any risk.
Other cloning vectors include:
- Yeast Artificial Chromosomes
- Retroviral Vectors
- Human Artificial Chromosomes
Cloning vectors are used to insert foreign DNA into another cell and create multiple copies for the same. The foreign DNA is replicated and expressed using the host cell machinery. It amplifies a single copy of DNA into multiple copies.
Also Read: DNA Cloning
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