Final answer:
The process of going from a primary product light chain to a mature light chain Ig involves somatic recombination in germ-line B cells. DNA recombinase excises and splices V and J segments, resulting in a unique variable chain in each differentiated B cell.
Step-by-step explanation:
The process of going from a primary product light chain to a mature light chain Ig involves somatic recombination. In germ-line B cells, an enzyme called DNA recombinase randomly excises variable (V) and joining (J) segments from the light chain gene, and then splices one V segment to one J segment. During RNA processing, all but one V and J segment are spliced out, resulting in over 10^6 possible VJ combinations. This leads to the production of a unique variable chain in each differentiated B cell, contributing to the diversity of antibody molecules.