PCR Cloning Method

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PCR cloning differs from traditional cloning in that the DNA fragment of interest, and even the vector, can be amplified by the Polymerase Chain Reaction (PCR) and ligated together, without the use of restriction enzymes. PCR cloning is a rapid method for cloning genes, and is often used for projects that require higher throughput than traditional cloning methods can accommodate. It allows for the cloning of DNA fragments that are not available in large amounts.

Typically, a PCR reaction is performed to amplify the sequence of interest, and then it is joined to the vector via a blunt or single-base overhang ligation prior to transformation. Early PCR cloning often used Taq DNA Polymerase to amplify the gene. This results in a PCR product with a single template-independent base addition of an adenine (A) residue to the 3' end of the PCR product, through the normal action of the polymerase. These "A-tailed" products are then ligated to a complementary T-tailed vector using T4 DNA ligase, followed by transformation. 

High-fidelity DNA polymerases are also now routinely used to amplify sequences with the PCR product containing no 3' extensions. The blunt-end fragments are joined to a plasmid vector through a typical ligation reaction or by the action of an "activated" vector that contains a covalently attached enzyme, typically Topoisomerse I, which facilitates the vector:insert joining. Some PCR cloning systems contain engineered "suicide" vectors that include a toxic gene into which the PCR product must be successfully ligated to allow propagation of the strain that takes up the recombinant molecule during transformation.

A typical drawback common to many PCR cloning methods is a dedicated vector that must be used. These vectors are typically sold by suppliers, like NEB, in a ready-to-use linearized format and can add significant expense to the total cost of cloning. Also, the use of specific vectors restricts the researcher's choice of antibiotic resistance, promoter identity, fusion partners, and other regulatory elements.

  • High efficiency, with dedicated vectors
  • Amenable to high throughput
  • Limited vector choices
  • Higher cost
  • Lack of sequence control at junction
  • Multi-fragment cloning is not straight forward
  • Directional cloning is difficult

PCR Cloning

Note that times are based on estimates for moving a gene from one plasmid to another. If the source for gene transfer is gDNA, add 2 hours to calculation for the traditional cloning method. Total time does not include transformation, isolation or analysis.