Most do not cause problems, but some cause diseases other than sickle-cell anemia. Figure 17.2 illustrates the location of some of the variant amino acids. Receptor and Transport Protein Dysfunctions Familial Hypercholesterolemia High levels of blood cholesterol can lead to blood vessel blockage and heart attacks at relatively early ages. Clots in the brain can lead to stroke. The problem for these individuals is an inability to transport the cholesterol into the cells where it is needed.
Cholesterol is transported in the blood as a lipoprotein .
When it reaches the liver, the necessary receptor for binding the lipoprotein has a modified structure that does not allow binding. Binding fails to occur and the lipoprotein cannot enter the liver cells. Hence, the cholesterol cannot be processed and remains in the blood. This is one of the more common genetic diseases among Caucasians. Individuals with the disease have a very thick, dry mucus that lines the airways and prevents the cilia from doing their cleansing job.