The main difference between plasmid and phagemid is that a plasmid is a small, extrachromosomal piece of DNA that can replicate independently of the bacterial chromosome, whereas a phagemid is a hybrid molecule that combines the properties of a plasmid and a bacteriophage.
Plasmids and phagemids are both small, circular pieces of DNA present in bacterial cells.
y Areas Covered
1. What is a Plasmid
– Definition, Components, Features
2. What is a Phagemid
– Definition, Components, Features
3. Similarities Between Plasmid and Phagemid
– Outline of Common Features
4. Difference Between Plasmid and Phagemid
– Comparison of Key Differences
Key Terms
Plasmid, Phagemid
What is a Plasmid
A plasmid is a small, circular piece of DNA that is present in many types of bacteria. As they are outside the bacterial chromosome, they are considered extrachromosomal DNA. Their size ranges from a few kilobases to several hundred kilobases. They have the ability to replicate independently of the bacterial chromosome. Moreover, they can be transferred between bacterial cells through various mechanisms. Plasmids have a smaller structure. They only contain a few components, including an origin of replication, a selectable marker, and one or more genes of interest.
The origin of replication is a sequence of DNA that is recognized by the bacterial replication machinery and allows the plasmid to replicate independently of the chromosome. The selectable marker gene is a gene that confers a selective advantage to the bacterial host, such as resistance to an antibiotic. They also contain components such as transcriptional and translational regulatory sequences, promoters, and terminators, which control the expression of the genes on the plasmid.
Plasmids can be used as vectors to transfer genes between different organisms. They also have the ability to be manipulated and transferred between bacterial cells. In addition, they can be modified to have certain specific genes of interest. They also can be used to study the regulation of gene expression and the mechanism of DNA replication and repair.
Plasmids can be manipulated in several ways, including cloning, site-directed mutagenesis, and genetic engineering. Furthermore, plasmids are more stable than phagemids.
What is a Phagemid
A plasmid is a hybrid molecule that combines the properties of a plasmid and a bacteriophage. A phagemid is a circular, double-stranded DNA molecule. Its size ranges from 5-10 kilobases. Phagemids have two main components: one is a plasmid backbone, and the other is a phage DNA fragment. The functions of a plasmid backbone are maintenance and replication. The phage DNA fragment contains genes that confer properties such as antibiotic resistance or fluorescence. The plasmid backbone has some components. It includes an origin of replication, a selectable marker, and multiple cloning sites. The phage DNA fragment contains genes that allow the phagemid to package its DNA into phage particles and infect host cells.
Phagemids have different functions. They allow the propagation and manipulation of DNA in a variety of ways. Phagemid can replicate when it is introduced into a bacterial cell. Phagemids are often used to generate large quantities of single-stranded DNA. These are used in DNA sequencing and site-directed mutagenesis. Phagemids are also used to construct gene libraries. In addition, they help in protein expression. They are useful in expressing recombinant proteins in bacterial cells either as fusion proteins with the phage coat proteins or as cytoplasmic proteins. Moreover, they help to display recombinant antibodies on the surface of the phage particles, allowing for the selection of high-affinity binders.
Similarities Between Plasmid and Phagemid
- Both plasmids and phagemids are circular DNA molecules that can exist separately from the bacterial chromosome.
- Both plasmids and phagemids are frequently useful as tools in genetic engineering.
- They can carry genes that confer various benefits to the host bacterium, such as antibiotic resistance, virulence factors, or metabolic capabilities.
Difference Between Plasmid and Phagemid
Definition
A plasmid is a small, extrachromosomal piece of DNA that can replicate independently of the bacterial chromosome, whereas a phagemid is a hybrid molecule that combines the properties of a plasmid and a bacteriophage.
Size
Plasmids range from a few kilobases to several hundred kilobases, while phagemids have a size ranging from 5-10 kilobases.
Components
Plasmids contain an origin of replication, a selectable marker, and one or more genes of interest, while phagemids have a plasmid backbone and a phage DNA fragment that contains genes for antibiotic resistance or fluorescence.
Stability
Plasmids are more stable than phagemids.
Replication
Plasmids replicate using their own replication machinery, while phagemids can replicate either as a plasmid or as a phage depending on the presence or absence of a helper phage.
Conclusion
Plasmids and phagemids are both small, circular pieces of DNA. The main difference between a plasmid and a phagemid is that a plasmid is a small, extrachromosomal piece of DNA that can replicate independently of the bacterial chromosome, whereas a phagemid is a hybrid molecule that combines the properties of a plasmid and a bacteriophage.
Reference:
1. “Plasmid.” National Genome Human Research Institute.
2. “Phagemid.” Science Direct.
Image Courtesy:
1. “Plasmid (English)” By User:Spaully on English wikipedia – Own work (CC BY-SA 2.5) via Commons Wikimedia
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