Phagemid can replicate both single-stranded and double-stranded DNA. The f1 origin of replication extracts from an f1 phage. Phagemid contains a special origin of replication termed as the f1 origin of replication. Phagemid, also termed as Phasmid, is a type of hybrid vector too. Thus, the use of a cosmid as a vector can facilitate the cloning, and the restriction enzyme digestion of the vector can then extract these fragments. Cosmids usually contain antibiotic resistance genes as markers for selection of transformants. cosQ site – involved in preventing the degradation of the DNA by DNases.Īlso, Cosmids can either replicate single-stranded DNA or double-stranded DNA using a suitable origin of replication.cosB site – engaged in holding the terminase.cosN site – involved in nicking the DNA strand by terminase activity.Therefore, the cos sites are vital for packaging of the DNA. Hence, they have cohesive or sticky ends that allow the plasmid to fit into the viral DNA. These cos sites are long fragments of DNA with 200 basepairs. Side by Side Comparison – Cosmid vs Phagemid in Tabular FormĪ Cosmid, referred as a hybrid plasmid, comprises cos sites extracted from Lambda phage particles and a plasmid. Similarities Between Cosmid and Phagemidĥ. Cosmids and Phagemids are either replicated alone as plasmids or are packaged into viral particles and then replicated. These are widely used especially in cloning genes responsible for the production of various proteins. Therefore, it is a hybrid vector while a Phagemid is a plasmid that contains an F1 origin of replication of the F1 phage.Ĭosmids and Phagemids are used for cloning purposes, especially to clone larger fragments of DNA.
A Cosmid contains a cos site and a plasmid. When a speaker calls it "a vector," they may be referring to either of its vector aspects or often both.Īrthropods: Members of a major group or phylum of invertebrate animals with hard exoskeletons, segmented bodies, and jointed appendages includes crustaceans, insects, spiders, etc.The key difference between Cosmid and Phagemid is on the type of sequences it contains. In such a situation, a plasmid vector may be regarded as serving as its own gene-therapy vector. Some transformation technologies, such as lipofectamine, enable the direct delivery of a DNA construct as therapy in a tissue. There is a possibility for confusion between the use of "vector" in gene therapy and its use in molecular biology more generally. Because the constructs can be extracted from the cells by purification techniques, transformation with a vector is a way of making a small number of DNA molecules in to a much larger one. A single cell that has been transformed with a vector will grow into an entire culture of cells, which all contain the vector, as well as any gene attached to it within the construct. An appropriate replication origin causes a cell to copy the construct along with the cell's chromosomes and to pass it along to its progeny. A vector in this sense is a DNA construct, such as a plasmid or a bacterial artificial chromosome, that contains an origin of replication. A "vector" in this sense is a vehicle for delivering genetic material such as DNA to a cell.įinally, in genetics more generally, DNA by itself may be regarded as a vector, for example in particular when it is used for cell transformation. In gene therapy, a virus itself may serve as a vector, if it has been re-engineered and is used to deliver a gene to its target cell. This sense of "biological vector" is the primary one in epidemiology and in common speech. Species of mosquito, for example, serve as vectors for the disease-causing West Nile Virus which the insects may ingest by feeding from an infected bird and regurgitate into a human, infecting him or her. Vectors: Traditionally in medicine, a vector is an organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another. A number of artificially constructed plasmids are used as cloning vectors. Some plasmids are capable of integrating into the host genome. Plasmid: Autonomously replicating, extrachromosomal circular DNA molecules, distinct from the normal bacterial genome and nonessential for cell survival under nonselective conditions. coli this permits cloning of larger DNA fragments (up to 45 kb) than can be introduced into bacterial hosts in plasmid vectors. Cosmids can be packaged in lambda phage particles for infection into E. Cloned sequences are more stable in fosmids than in multi-copy vectorsĬosmid: Artificially constructed cloning vector containing the cos gene of phage lambda. Fosmid: A low-copy-number cosmid vector that is based on the Escherichia coli F-factor replicon.