Final answer:
The statement that each class of immunoglobulin is made from a different gene is false. The diversity of antibodies is due to gene segment rearrangements and post-translational modifications rather than each antibody being encoded by a unique gene.
Step-by-step explanation:
The statement that all classes of immunoglobulins are made from different genes is false. While it is true that immunoglobulins (Ig), also known as antibodies, vary widely in their antigen binding properties, this diversity is not solely due to each antibody being encoded by its own unique gene. Instead, the diversity is largely due to the rearrangement of gene segments encoding antibody polypeptides at the level of DNA. This process results in the production of an enormous variety of antibody molecules, each with the potential to bind a specific antigen. The human immune system does this through a complex process involving the mutation and recombination of approximately 300 different gene segments encoding the light and heavy chain variable domains in precursor B cells. Antibody diversity also benefits from post-translational modifications of these polypeptide chains. These diverse variable domains interact to form the antibody binding site, which ensures that antibodies can specifically target a variety of pathogens. The constant domains of the heavy chain remain the same within each antibody class, such as IgM, IgG, IgA, IgD, and IgE, which determine the immunological actions of the antibody.