Final answer:
The statement is false; VDJ rearrangement occurs during the maturation of B cells as part of their commitment to the B cell lineage, not before.
Step-by-step explanation:
The statement that 'Cells undergo VDJ rearrangement before they commit to the B cell lineage' is false. VDJ recombination is a process that takes place during the maturation of B cells, not before they have committed to the B cell lineage. In germ-line B cells, the variable regions of immunoglobulin genes consist of multiple Variable (V), Diversity (D), and Joining (J) segments. An enzyme known as DNA recombinase is responsible for randomly excising these segments from the heavy chain and light chain genes. In the case of the light chain gene, DNA recombinase slices one V segment with one J segment, which then undergo additional mRNA splicing during RNA processing. This recombination and splicing results in a significant number of possible VJ combinations, contributing to the production of a vast array of unique antibody molecules capable of targeting a wide variety of antigens. The constant region of the antibody remains unchanged, providing a stable structure for the variable region, which is responsible for antigen binding.