Final answer:
In the light chain of an antibody, the functional variable region is formed by the coming together of a V segment and a J segment.
Step-by-step explanation:
In the light chain of an antibody, the functional variable region is formed by the coming together of two gene segments: a variable (V) segment and a joining (J) segment.
During the development of the functional antibody, an enzyme called DNA recombinase randomly excises most of the V and J segments, and splices one V segment to one J segment. This recombination and splicing process generates over 106 possible combinations, resulting in each differentiated B cell typically having a unique variable chain.