Regulation of average length of complex PCR product.

A method to achieve the preference towards longer products during PCR is described. The extent of this preference can be adjusted by slight variation of the PCR conditions. Being combined with the natural tendency of PCR to amplify shorter fragments more efficiently than longer ones, it allows one to regulate the average length of the complex PCR product over a very wide range to make it most suitable for further manipulations. The technique can be used for amplifying any complex DNA sample.