Investigation of genetic disorders, such as abetalipoproteinemia and hypobetalipoproteinemia, have been of immense support in defining the indispensable role of microsomal triglyceride transfer protein (MTTP) and Apo B-48 for the gut and Apo B-100 for the liver, respectively (5, 6, 7, 8, 9). The gene discussed is MTTP; the disease is abetalipoproteinemia.