Final answer:
P and N nucleotides are introduced into the immunoglobulin genes' DNA during B cell maturation to create diverse antibody molecules. The rearrangement involves DNA recombinase assembling different combinations of V, D, J segments with the consistent C region. This genetic diversity allows for the production of antibodies with unique antigen-binding sites.
Step-by-step explanation:
P and N nucleotides are introduced into the DNA during the recombination of immunoglobulin genes. This process, which involves the rearrangement of V (variable), D (diversity), and J (joining) segments, leads to the production of a vast diversity of antibodies essential for the immune response. An enzyme called DNA recombinase mediates the recombination, and this random genetic shuffling contributes to the ability of B cells to generate a unique set of immunoglobulins with varying antigen-binding sites.
In germ-line B cells, the variable region of the light chain gene contains multiple V and J segments. DNA recombinase facilitates the excision of these segments, joining one V to one J segment, which during RNA processing, further narrows down to a single V and J segment combination. This recombination, along with additional splicing, may result in more than 106 (one million) possible VJ combinations.
The constant (C) region of the immunoglobulin antibody molecule remains the same across all antibodies, providing a stable framework that does not influence antigen binding. The introduction of P and N nucleotides is a key aspect in generating the necessary diversity for recognizing and responding to a wide array of antigens.