A method for providing a hybrid polypeptide having an activity of interest, by i) performing PCR amplification using an uncharacterized DNA sample and oligonucleotide primers with homology to one or more known genes encoding a polypeptide exhibiting said activity of interest, to obtain one or more PCR products, ii) linking the obtained PCR products to a 5′ structural gene sequence and a 3′ structural gene sequence, wherein the 5′ and 3′ structural gene sequences are derived from one or more genes encoding a polypeptide exhibiting said activity of interest, to form hybrid DNA sequences, iii) expressing the resulting hybrid DNA sequences, and iv) screening the hybrid polypeptides to identify a sequence encoding a polypeptide exhibiting said activity of interest or a related activity.