Vector: properties, types and characteristics

Vector: properties, types and characteristics


  1. Introduction
  2. Properties of good vector
  3. Types of vector
  4. Plasmid vector
  5. Cosmids
  6. Phagemids
  7. Phage vector or Bacteriophage vector
  8. Artificial chromosome vector
  9. Shuttle vector


  • It is a biological tool in rDNA technology.
  • It is used for the delivery of desired foreign DNA into the host cell.
  • A vector is a DNA molecule that have the ability to replicate autonomously in the host cell and into which DNA fragment to be cloned.

Properties of an ideal vector

  • It should be replicate autonomously.
  • A vector should be less than 10 KB in size.
  • It should be easily isolated and purify.
  • It should be easily introduced into the host cell.
  • It should have suitable marker genes.
  • Vector should consists a unique target sites and recognition sites for various restriction enzymes.
  • It should have the capability to incorporate either itself or the DNA insert in the Genome of the host cell.

Types of vector

Vectors are of two types:

    • Cloning vector
    • Expression vector

Cloning vectors

  • Cloning vectors are small piece of DNA which have the ability and used to introduce foreign gene of interest into the host cell.
  • They can be stably maintained insides the host cell.
  • Cloning vector are generally used to obtain multiple copies of desired foreign gene.
  • Example- Plasmid, Cosmid and Phages, BACs, YACs.
  • These type of vectors generally contains selectable marker, origin of replication and a restriction site.

Expression vector

  • Expression vector is a type of vector which not only introduces a gene of interest into the host cell but also aids in the analysis of the foreign gene via relevant protein product expression.
  • It is type of vector which is used to obtain or analyses the gene product, which may be RNA or protein of the inserted desired gene.
  • Example- Only plasmid vector.
  • Expression vector contains enhancer, promoter region, start/stop codon, transcription initiation, selectable marker, ori sites, and restriction site.

Plasmid vector

  • A plasmid is a naturally occurring extrachromosomal double stranded DNA, circular DNA.
  • It replicates autonomously within bacterial cell.
  • Plasmid carries an origin of replication.
  • Plasmid vectors are the simplest cloning vectors.
  • It is most widely used for gene cloning.

Characteristics of Plasmid vector:

  • It contains an ori site or origin of replication.
  • It also Contain selective marker such as antibiotic resistance, blue white screening).
  • Small in size (1.0 to 250kb)
  • Contains multiple cloning site.
  • Easily isolated from the host cell.

Examples of plasmid vectors are:

    1. pBR322
    2. pUC 18/19

pBR322 vector

  • It is one of the first vectors to be developed by Boliver and Rodriguez in 1977.

pBR322 vector

The name pBR322 denotes the following:

    1. P- plasmid
    2. B- Boliver
    3. R- Rodriguez
  • 322- Differentiate it from the other plasmid produced in the same laboratory E.g. – pBR325, pBR327, etc.
  • It is 4363 base pair long.

It carries two sets of antibiotic resistance gene:

    • Ampicilli
    • Tetracycline

It contains only single or unique recognition site for 12 different restriction enzymes:

    • Pst I
    • Sac I
    • Pvu I

pUC 18/19

  • It is derivative of pBR322.
  • Much smaller (~ 2.7kb).
  • Ampicillin resistance gene (bla).
  • ColE1 origin of replication.
  • It is 2,686bp long.

pUC19 vector

The name pUC18/19 derived from:

    1. P- Plasmid.
    2. UC- university of California.

Cosmids vector

  • It is a type of hybrid plasmid.
  • It contains lambda phage cos sequence.
  • Cosmids = cos sites + plasmid.
  • Genomic size of cosmids is about 30 to 52 kb.
  • If they have suitable origin of replication than they can replicate as Plasmid within the host cells, E.g.- SV40 Ori, ColE1 ori.
  • It also contains selectable marker such as Ampicillin resistance gene.
  • Collins and Hohn in 1978 was first to described cosmids.

Phagemid Vector

  • A plasmid vector which contains an origin of replication from a phage, in addition to that of the plasmid, is termed as Phagemids.
  • pBlue script SK (+/-) is a type of phagemid vector of 2,958 bp derived from the pUC19.

It consists of the following:

    1. ColE1 ori
    2. Phage f1 (M13) origin of replication.
    3. A small portion of lacZ gene.
    4. MCS within lacZ Gene from Lac promoter.
    5. Phage T7 and T3 promoter sequence.
    6. Ampicillin gene for Ampicillin resistance.

Phage vector or Bacteriophage vector

  • Bacteriophages are viruses that attacks bacteria.
  • The Phages are simple in structure.
  • It consists of DNA molecules having several gene for replication which is surrounded by Capsid.

On the basis of structure bacteria phases are of two types:

    1. Head and Tail Phages- E.g.: lambda phage.
    2. Filamentous phage- E.g.: M13 phage.

Lambda phage vectors

  • Its genome size is about 48,502 bp.
  • It contains origin of replication, genes for head and tail protein and enzymes for DNA replication
  • It has more than one recognition sequence for almost all the restriction enzymes.
  • It should be larger than 38 kb and smaller than 52 kb to packaged into phage particles.

M13 phage vectors

  • M13 vectors are used to obtain single- stranded copies of cloned DNA.
  • It is 6407 nucleotides long.
  • It is circular and 6.4kb in size.
  • M13 vector only cause infection in F+ and F’ cells.
  • It is used to produce several copies of M13 mp series of vectors.
  • Example- M13mp8, M13mp9 etc.

Artificial chromosome vectors

  • Artificial chromosomes are circular or linear vectors.
  • They are stably maintained in, usually 1 to 2 copy per cell.

There are several types of such vectors:

    1. Bacterial artificial chromosomes (BAC).
    2. Yeast artificial chromosomes(YAC).
    3. Mammalian artificial chromosomes(MAC).
    4. Human artificial chromosome (HAC).

Shuttle vector

  • Shuttle vectors are created to replicates in cell of different type of species.
  • They contain two origin of replication, in which one is particular for each host species, also those genes required for their replication and not provided by the host cell.
  • This type of vectors are developed by recombinant techniques.

Reference and Sources

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Vector: properties, types and characteristics

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