Correct Option: C

Allelic exclusion has been observed most often in genes for cell surface receptors and has been extensively studied in immune cells such as B lymphocytes. In B lymphocytes, successful heavy chain gene rearrangement of the genetic material from one chromosome results in the shutting down of rearrangement of genetic material from the second chromosome. If no successful rearrangement occurs, rearrangement of genetic material on the second chromosome takes place. If no successful rearrangement occurs on either chromosome, the cell dies. As a result of allelic exclusion, all the antigen receptors on an individual lymphocyte will have the same amino acid sequence in the variable domain of the heavy chain protein. As the specificity of the antigen receptor is modulated by the variable domain of the light chain encoded by one of the immunoglobulin light chain loci, the specificities of B cells containing the same heavy chain recombination event can differ according to their light chain recombination event.