The present invention is directed to the concept of sectoring antibody gene segment repertoires in order to enable the development of novel, synthetic antibody chain repertoires not seen in nature. The present invention is also directed to the realisation of the inventors that sectoring can also alter gene segment expression by providing new arrangements of gene segment clusters relative to other gene segments and regulatory elements in transgenic immunoglobulin loci, thereby providing for new synthetic antibody chain sequence repertoires. The invention also relates to gene segment inversion.
