Question

Gene rearrangements of the light chain include all of the following, except:

a. At least four possible attempts for a successful rearrangement.
b. Rearrangement of the κ genes first, and then the λ genes.
c. If no successful rearrangements are made, apoptosis will result.
d. Rearrangement of the μ genes first, and then the δ genes.

Answer 1

The exception in the gene rearrangements of the light chain is the b. rearrangement of the μ (mu) genes first, which pertains to the heavy chain rather than the light chain.

Step-by-step explanation:

Gene rearrangements of the light chain include several processes, but the rearrangement of the μ genes does not occur during light chain gene rearrangement. Instead, the light chain is composed of variable (V) and joining (J) segments in B cells. The rearrangement process involves DNA recombinase excising these V and J segments to create a diverse array of possible variable regions for antibodies. This diversity is crucial for the immune system's ability to recognize a wide range of antigens.

The correct order starts with the rearrangement of the κ (kappa) genes first. If unsuccessful, the λ (lambda) genes will rearrange. If neither results in a successful combination, apoptosis may occur to eliminate the non-functional cell. In this process, the variability of antibody molecules is generated at the DNA level, ensuring that each differentiated B cell typically produces a unique antibody. However, rearrangement of the μ (mu) genes first followed by the δ (delta) genes, as suggested in option d, actually pertains to the heavy chain rather than the light chain, making it the exception.