Final answer:
Changes in cleavage and polyadenylation affect protein products by altering mRNA stability and translation, impacting the type of proteins, such as antibodies, whether they are membrane-bound or secreted. This is determined by alternative RNA splicing in B cells, leading to differential processing and post-translational modifications.
Step-by-step explanation:
Changes in cleavage and polyadenylation can significantly affect protein products by altering mRNA stability and translation efficiency, which ultimately influences the type and quantity of proteins produced, such as antibodies. Antibodies can be either membrane-bound or secreted, and this is determined by alternative RNA processing events that occur in B cells. During B cell maturation, specific mRNA sequences coding for membrane-bound or secreted antibodies are generated through alternative RNA splicing. Such differential processing can lead to the production of a membrane-bound B cell receptor or its secreted form, an antibody, respectively. The secreted antibody is produced when RNA encoding the B cell receptor is processed to include a hydrophobic region that acts as a signal peptide, directing the nascent polypeptide to the endoplasmic reticulum for secretion. Alternatively, omission of this sequence in the mRNA leads to the production of a receptor that remains associated with the B cell membrane. In both cases, post-translational modifications, including those governed by the Signal Hypothesis, play a critical role in determining the protein's ultimate destination and function.