High fidelity pcr cloning

Abstract

The present invention describes a methodology for generating high fidelity PCR products, and also cloning of such high fidelity PCR products in a suitable vector. Generation of polymerase-induced mutant fraction of target sequences during PCR amplification is linearly proportional to the number of doublings of the target sequences. Thus the high fidelity PCR products are generated by minimizing the number of doublings of the target nucleic acid sequences during PCR amplification. Minimization of number of doublings of the target sequences is achieved by reducing the number of cycles of PCR amplification of the target sequences. The high fidelity PCR products thus obtained are then cloned into a suitable vector. As an example, a 960 bp target sequence from DNA was PCR-amplified only for 3 cycles, and it was then directly cloned into a positive selection cloning vector pRGR2Ap. The functional analysis of the inserts in all clones showed that the clones carried functionally wild-type DNA fragments, and hence the inserts most probably carry no mutation. Cloning of PCR products obtained from 3 cycles of amplification, instead of 30 cycles of amplification, theoretically achieves 10-fold reduction of mutations in the cloned fragments. The invention also contemplates cloning of a target cDNA obtained by primer extension.