The key difference between cloning vector and expression vector is that cloning vector carries a foreign DNA fragment into the host cell while expression vector facilitates the expression of genes into proteins.
Vector is an important term in molecular biology. In recombinant DNA technology, the main role of a vector is to provide a mode of transport to a useful DNA fraction to be inserted into a host cell. Moreover, it is a DNA molecule used to carry a foreign DNA fragment artificially into a host cell to be expressed or replicated. Most used vectors are plasmids, viral vectors, cosmids and artificial chromosomes. Cloning vector and expression vector are two types of vectors classified based on their applications.
CONTENTS
1. Overview and Key Difference
2. What is a Cloning Vector
3. What is an Expression Vector
4. Similarities Between Cloning Vector and Expression Vector
5. Side by Side Comparison – Cloning Vector vs Expression Vector in Tabular Form
6. Summary
What is a Cloning Vector?
A cloning vector is a fraction of DNA that can be used to insert a foreign DNA molecule and has the ability to be inserted into a host for cloning purpose. An ideal characteristic of a cloning vector is easy insertion/removal of the DNA fragment by restriction enzyme treatment and ligating enzyme treatment. In this aspect, frequently used cloning vectors are the genetically engineered plasmids.
Figure 01: Cloning Vector
A cloning vector should have a multiple cloning site, a selectable marker gene and a reporter gene. The purpose of a cloning site is to provide a place for cloning to occur. A selectable marker gene helps identifying successful recombinants after cloning and a reporter gene allows screening and identifying the correct recombinant among the recombinants after cloning. The cloning vector does not necessarily help to express a protein which the foreign DNA encodes. Thus, the sole purpose of the cloning vector is to carry foreign DNA to the host.
What is an Expression Vector?
Expression vector, also called expression construct, is a type of vector used for the expression of proteins inside the host cell. Like any vector, this should also contain the main parts a multiple cloning site, a marker gene and a reporter gene. The vector introduces a new gene into the host and using the host’s protein synthesis mechanism, it allows the gene to be expressed into the host. Moreover, its initial focus is to make stable m-RNA and thereby make proteins. One good example is the commercial production of insulin. The insulin gene is introduced to a bacterial plasmid and inserted back into E. coli bacteria body, allowing the plasmids to multiply and allowing the E. coli to grow, secreting insulin which can be collected and used.
Figure 02: Expression Vector
Furthermore, an expression vector should have a strong promoter region, a correct translation initiation sequence and a correct terminator codon and a sequence. Expression vectors have numerous applications in producing peptides and proteins for the pharmaceutical industry such as producing insulin, growth hormone, antibiotics, vaccines, antibodies. Moreover, expression vectors help in enzyme production in food and garment industries. Not only that, expression vectors are essential in producing transgenic plants such as golden rice, insect resistant plants, herbicide-resistant plants, etc.
What are the Similarities Between Cloning Vector and Expression Vector?
- Cloning vector and expression vector are two types of vectors we use in recombinant DNA technology and genetic engineering.
- Both contain a marker gene and a reporter gene.
- Moreover, they consist of multiple cloning sites.
- Also, they have an origin of replication, and the ability to self replicate.
What is the Difference Between Cloning Vector and Expression Vector?
A cloning vector is a small DNA molecule that carries a foreign DNA fragment into the host cell while expression vector is a type of vector that facilitates the introduction, expression of genes and production of proteins. So, this is the key difference between cloning vector and expression vector. Furthermore, another significant difference between cloning vector and expression vector is that a cloning vector introduces a foreign DNA fragment into a host while expression vectors express the introduced gene by producing the relevant protein.
Furthermore, cloning vector consists of an origin of replication, restriction sites, and a selectable marker. While, the expression vector contains enhancers, promoter region, termination codon, transcription initiation sequence, an origin of replication, restriction sites, and a selectable marker. Therefore, this is also a difference between cloning vector and expression vector. Besides, plasmids, bacteriophages, bacterial artificial chromosomes, cosmids, mammalian artificial chromosomes, yeast artificial chromosome, etc, are examples of cloning vectors. Meanwhile, expression vectors are mostly plasmids.
Summary – Cloning Vector vs Expression Vector
Based on their function in molecular biology, there are two types of vectors as cloning vector and expression vector. A cloning vector is a small DNA molecule that delivers foreign DNA into the host cell. There are different types of cloning vectors such as plasmids, bacteriophages, bacterial artificial chromosomes, cosmids, and mammalian artificial chromosomes. In contrast, an expression vector is a plasmid that introduces the gene of interest into the host cell and facilitates the gene expression to obtain the protein product. Expression vectors are plasmids. Thus, this is the summary of the difference between cloning vector and expression vector.
Reference:
1. “Expression Vector.” Wikipedia, Wikimedia Foundation, 30 Apr. 2019, Available here.
2. Lodish, Harvey. “DNA Cloning with Plasmid Vectors.” Molecular Cell Biology. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
Image Courtesy:
1. “BACs cloning vectors Chem114A” By Zoragon7 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Amp replica plate” By Tinastella – (CC BY-SA 3.0) via Commons Wikimedia
