Pleiotropy

A single genetic disorder can produce several symptoms, a phenomenon called pleiotropy (plee-o-trope-ee). Family members who have different symptoms can appear to have different illnesses.

Pleiotropy is seen in genetic diseases that affect a single protein found in different parts of the body. This is the case for Marfan syndrome, an autosomal dominant defect in an elastic connective tissue protein called fibril-lin. The protein is abundant in the lens of the eye, in the aorta, and in the bones of the limbs, fingers, and ribs. This molecular-level abnormality explains the Marfan syndrome symptoms of lens dislocation, long limbs, spindly fingers, and a caved-in chest. The most serious symptom is a life-threatening weakening in the aorta wall, which sometimes causes the vessel to suddenly burst. If the weakening is found early, a synthetic graft can be used to patch that part of the vessel wall, saving the person's life. Clinical Application 14.1 discusses another pleiotropic disorder, porphyria.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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