IN VITRO SORTING METHOD

The invention relates to a method for isolating one or more genetic elements encoding a gene product having a desired activity, comprising the steps of: (a) compartmentalising genetic elements into microcapsules; (b) expressing the genetic elements to produce their respective gene products within the microcapsules; (c) sorting the genetic elements which produce the gene product having a desired activity. The invention permits the in vitro evolution of nucleic acids by repeated mutagenesis and iterative applications of the method of the invention.