A method for generating a variant library of DNA sequences starting from at least one DNA starting sequence and including the steps: a) selecting at least two mutation sites in the starting sequence; b) dividing the DNA starting sequence into at least two sequence segments such that at least two of these sequence segments each contain at least one of the mutation sites; c) amplifying the sequence segments by polymerase chain reaction using at least five different oligonucleotides, where at (i) least one of the oligonucleotides can attach to each mutation site; (ii) at least two of the oligonucleotides can attach to at least one mutation site, and (iii) mutations are introduced, via mismatch positions, into the PCR amplificates by the oligonucleotides at the mutation sites where at least two mutations are introduced at at least one of the mutation sites; and d) linking the amplificates to give DNA sequences.