<p>The present invention provides an in vitro method for obtaining a library of polynucleotides encoding antibodies, derivatives thereof or fragments thereof, comprising the step of performing random mutagenesis of a polynucleotide encoding the variable region of a heavy chain and/or the variable region of a light chain of a light chain, wherein random mutagenesis is performed on a library of polynucleotides comprising a sequence encoding the variable region of a heavy chain and/or the variable region of a light chain; and wherein the random mutagenesis process creates randomly distributed mutations along at least 70% of the sequence encoding the variable region.</p>
