Compositions and methods are provided for selection and enrichment of a target gene from a library of polynucleotide sequences such as might be formed from a genome or by random mutagenesis of a genetic sequence. The selection and enrichment occurs in aqueous droplets formed in an emulsion that compartmentalize individual polynucleotides from the library or a plurality of polynucleotides that may include polynucleotides not derived from the library, transcription and translation reagents and optionally additional chemical and enzyme reagents. The selection and enrichment method utilizes a polynucleotide adaptor which when ligated to the polynucleotide fragment enables amplification to occur in the presence of an adaptor specific primer.