Plasmid vs Vector
Transfer of foreign DNA to selected host and allow it to duplicate in a host cell is described as genetic engineering. Most DNA fragments cannot be self-replicated in another host cell. Therefore, it needs an additional self-replicating DNA to combine with it. Mostly, host organism may be a bacterium such as Escherichia coli (E-coli) (Wilson and walker, 2003). Vector and plasmids are frequently used two words in genetic engineering.
This self-replicating DNA fragment is called cloning vector. After the DNA fragment has been linked to a suitable vector, it is called recombinant DNA. This recombinant DNA technology is applied in various areas such as in medicine, biotechnology etc.
There are several cloning vectors which are extra chromosomal factors including plasmids and bacteriophages. Cloning vectors should have special characteristics such as resistant to damages, ease to manipulation, and amount of DNA sequence they can accommodate. Cloning vector should have origin of DNA replication, which ensures that the plasmid will be replicated by the host cell. There are several vectors such as virus-based vectors, cosmid based vectors, yeast artificial chromosome (YAC) vectors. Vectors can be manipulated artificially after ligation and digestion reaction series. As an example, pBR322 is one of the plasmids that is widely adopted (Wilson and walker, 2003).
Plasmids that are used for the cloning in eukaryotic cells need a vector that has an eukaryotic origin of replication and marker genes that are expressed in eukaryotic cell.
Plasmid is a small circular DNA element, and it is considered as an extra chromosomal element. This small DNA element carries several genes, but lesser amount than in chromosomal DNA. Plasmid size can be varied from less than 1.0 kb to more than 200 kb, but the number of plasmid in a cell is a constant from generation to generation. These are not essential for the function of bacteria, where they reside, but these genes give extra survival to bacteria.
These genes are responsible for antibiotic resistance and metabolism of some substrates such as β-galactosidase (Wilson and walker, 2003). These plasmids have a higher rate of replicating ability as an example in Escherichia coli. These have high potential to use as vectors. At certain conditions, these plasmids may integrate to the plasmids and replicate with the bacterial chromosome.
What is the difference between Vector and Plasmid ?
• Vector can be derived from a plasmid.
• Vector is a plasmid or manipulated artificially after ligation and digestion reaction series, whereas a plasmid naturally occurs in bacterial cells.
• There are several vectors, which can be used in recombinant DNA, whereas all plasmids may not be used directly in recombinant DNA technology.
• Vector is artificially incorporated into a cell, whereas plasmid is naturally occurring in a cell.
• Product, which is coded by a vector, is essential to human, whereas product, which is coded by plasmid, are not essential for the function of bacteria, where they reside, but these genes give extra survival to bacteria.
Wilson. K., and Walker. J., Practical biochemistry: Principles and techniques, Cambridge University press, Cambridge.
Joshi, P, genetic engineering and its application