Final answer:
Site specific recombination in B cells involves the joining of variable (V) and joining (J) segments of immunoglobulin light chain genes to create diverse antibodies.
Step-by-step explanation:
The regions that site specific recombination joins in the rearrangement of immunoglobulin light chain genes are the variable (V) and joining (J) segments. In the development of B cells, DNA recombinase specifically excises and joins these V and J segments to generate a diverse array of antibodies.
Each B cell hence will typically display a unique immunoglobulin with a unique variable region capable of binding different antigens, a mechanism critical for the adaptive immune response.