Final answer:
DNA recombinase is required to join V and J segments in B cells, creating a unique variable region for antibodies via random excision and splicing.
Step-by-step explanation:
An enzyme called DNA recombinase is required to join V (variable) with J (joining) to rearrange the light chain during B cell development.
This recombination process allows the generation of a diverse repertoire of antibodies, by randomly excising most of the V and J segments from the gene and splicing one V segment to one J segment. Splicing at the mRNA level further refines this diversity, resulting in over 106 possible VJ combinations and thus a unique variable region for each antibody produced by a differentiated B cell.