Abstract: The present invention relates to a non-PCR (polymerase chain reaction) process, particularly a transcription-based amplification method, for amplifying and cloning sequences containing a variable domain sequence such as an immunoglobulin variable domain sequence from the immunological gene repertoire. The present invention comtemplates the expression of antibody library in either in an in vivo expression vector or in an in vitro transcription/translation system. Isolation of a gene coding for a receptor having the ability to bind a preselected ligand and receptors produced by the gene isolated by the method is also contemplated.