vector

Examples of vector in the following topics:

• Vectors for Genomic Cloning and Sequencing

  • The four major types of vectors are plasmids, viral vectors, cosmids, and artificial chromosomes.
  • The vector itself is generally a DNA sequence that consists of an insert (transgene) and a larger sequence that serves as the "backbone" of the vector.
  • Simpler vectors called transcription vectors are only capable of being transcribed but not translated: they can be replicated in a target cell but not expressed, unlike expression vectors.
  • Transcription vectors are used to amplify their insert.
  • In the case of plasmids utilized as transcription vectors, incubating bacteria with plasmids generates hundreds or thousands of copies of the vector within the bacteria in hours.

• Shuttle Vectors and Expression Vectors

  • Cloning vectors, which are very similar to expression vectors, involve the same process of introducing a new gene into a plasmid, but the plasmid is then added into bacteria for replication purposes.
  • A shuttle vector is a vector that can propagate in two different host species, hence, inserted DNA can be tested or manipulated in two different cell types.
  • Shuttle vectors can be used in both eukaryotes and prokaryotes.
  • One of the most common types of shuttle vectors is the yeast shuttle vector that contains components allowing for the replication and selection in both E. coli cells and yeast cells.
  • The pGEX-3x plasmid is a popular cloning vector.

• Plasmids as Cloning Vectors

  • The four major types of vectors are plasmids, viral vectors, cosmids, and artificial chromosomes.
  • The purpose of a vector is to multiply the insert, although expression vectors also drive the translation of the multiplied insert.
  • Expression vectors require translation of the vector's insert, thus requiring more components than simpler transcription-only vectors.
  • Promoter: a necessary component for all vectors, used to drive transcription of the vector's transgene.
  • The pGEX-3x plasmid is a popular cloning vector.

• Arthropods as Vectors

  • Arthropods are capable of serving as vectors, indicating that they play a major role in disease transmission.
  • Arthropods that serve as vectors include mosquitoes, fleas, sand flies, lice, ticks, and mites.
  • These types of vectors are considered to be hematophagous.
  • Fleas are another type of arthropod vector that transmit numerous diseases.
  • The oriental rat flea is an example of an arthropod vector as it is the primary vector of plague.

• Hosts for Cloning Vectors

  • A very large number of host organisms and molecular cloning vectors are in use, but the great majority of molecular cloning experiments begin with a laboratory strain of the bacterium E. coli (Escherichia coli) and a plasmid cloning vector.
  • Specialized applications may call for specialized host-vector systems.
  • Alternatively, if replication of the DNA in different species is desired (for example transfer of DNA from bacteria to plants), then a multiple host range vector (also termed shuttle vector) may be selected.
  • In practice, however, specialized molecular cloning experiments usually begin with cloning into a bacterial plasmid, followed by subcloning into a specialized vector.
  • Whatever combination of host and vector are used, the vector almost always contains four DNA segments that are critically important to its function and experimental utility--(1) an origin of DNA replication is necessary for the vector (and recombinant sequences linked to it) to replicate inside the host organism, (2) one or more unique restriction endonuclease recognition sites that serves as sites where foreign DNA may be introduced, (3) a selectable genetic marker gene that can be used to enable the survival of cells that have taken up vector sequences, and (4) an additional gene that can be used for screening which cells contain foreign DNA.

• Recombinant DNA Technology

  • To improve the ratio of recombinant to non-recombinant organisms, the cleaved vector may be treated with an enzyme (alkaline phosphatase) that dephosphorylates the vector ends.
  • Cells harboring the vector will survive when exposed to the antibiotic, while those that have failed to take up vector sequences will die.
  • Modern bacterial cloning vectors (e.g. pUC19) use the blue-white screening system to distinguish colonies (clones) of transgenic cells from those that contain the parental vector.
  • DNA of interest is ligated into a vector.
  • The vector is then transformed into competent cell (bacteria).

• Infectious Disease Transmission

  • Transmission of infectious diseases may also involve a vector.
  • Vectors may be mechanical or biological.
  • Biological vectors are usually, though not exclusively, arthropods, such as mosquitoes, ticks, fleas, and lice.
  • Vectors are often required in the life cycle of a pathogen.
  • A common strategy used to control vector borne infectious diseases is to interrupt the life cycle of a pathogen by killing the vector.

• Obtaining DNA

  • Although a very large number of host organisms and molecular cloning vectors are used, the great majority of molecular cloning experiments begin with a laboratory strain of the bacterium E. coli (Escherichia coli) and a plasmid cloning vector.
  • The cloning vector is treated with a restriction endonuclease to cleave the DNA at the site where foreign DNA will be inserted.
  • Typically, this is done by cleaving the vector DNA and foreign DNA with the same restriction enzyme.
  • Most modern vectors contain a variety of convenient cleavage sites that are unique within the vector molecule (so that the vector can only be cleaved at a single site) and are not located within the gene of interest to be cloned.
  • Cells harboring the cloning vector will survive when exposed to the antibiotic, while those that have failed to take up cloning vector will die.

• Selection

  • Subsequently, these fragments are then combined with vector DNA to generate recombinant DNA molecules.
  • Experimental scientists deal with this issue through a step of artificial genetic selection , in which cells that have not taken up DNA are selectively killed, and only those cells that can actively replicate DNA containing the selectable marker gene encoded by the vector are able to survive.
  • Cells harboring the vector will survive when exposed to the antibiotic, while those that fail to take up vector sequences die.

• Plant Virus Life Cycles

  • Plant viruses are often spread from plant to plant by organisms known as vectors.
  • Plant viruses are often spread from plant to plant by organisms (vectors).
  • These are normally insects, but some fungi, nematode worms and single-celled organisms have been shown to be vectors.
  • When control of plant virus infections is considered economical, (for perennial fruits for example), efforts are concentrated on killing the vectors and removing alternate hosts such as weeds.