One way to achieve variable region diversity in the antibodies produced by B cells is by somatic mutation. Individual nucleotides in rearranged variable regions are replaced with other bases (point mutations), which can change the structure of the antibody-binding site and thus change its ability to recognize antigen. In our lab we use a gene construct (HUG-1) composed of a mouse VDJ region and a human constant region. We study somatic mutation by sequencing hybridomas generated from transgenic mice immunized with the dansyl antigen (the antigen recognized by the transgene). Hybridomas with mutations in their variable regions are tested by Enzyme-Linked Immunosorbent Assay (ELISA) to ascertain whether the mutated antibodies had improved avidity antigen binding for the dansyl antigen.