(EN) A method for gene shuffling to form a mutant or chimeric gene, the method conmprising: (a) assigning one or more segments of one or more genes based on regions of encoded amino acid sequence; (b) amplifying the one or more assigned segments of the gene using primers specific for each segment; and (c) causing recombination of the one or more amplified segments to form a mutant or chimeric gene. An oligonucleotide primer suitable for use in gene shuffling, the primer having a non-degenerate core based on a segment or template of a gene to be amplified, and the core being flanked by both 5' and 3' degenerate ends.