Gene site saturation mutagenesis

A method for producing a set of progeny polynucleotides, comprising the steps of

• (a) providing copies of a template polynucleotide, each comprising a plurality of codons that encode a template polypeptide sequence;
• and
• (b) for each codon of the template polynucleotide, performing the steps of
• (1) providing a set of degenerate primers,
• wherein each primer comprises a degenerate codon corresponding to the codon of the template polynucleotide and at least one adjacent sequence that is homologous to a sequence adjacent to the codon of the template polynucleotide;
• (2) providing conditions allowing the primers to anneal to the copies of the template polynucleotides;
• and
• (3) performing a polymerase elongation reaction from the primers along the template;
• thereby producing progeny polynucleotides, each of which contains a sequence corresponding to the degenerate codon of the annealed primer;
• thereby producing a set of progeny polynucleotides.