According to the Human Genome Project, both environmental and genetic factors influence the development of any disease, including hereditary diseases. A hereditary disease or genetic disorder, is caused by abnormalities in a person's genetic material or genome. The four classifications of genetic disorders include single-gene, multifactorial, chromosomal and mitochondrial. There are numerous types of hereditary diseases but relatively common types include Marfan syndrome, sickle cell anemia and Tay-Sachs disease.
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According to the National Marfan Foundation or NMF, Marfan syndrome is a genetic disorder of the connective tissue. Connective tissue is responsible for binding together the body's various parts and it helps dictate how the body grows and develops. Because connective tissue is found in almost all parts of the body, Marfan syndrome can have wide-ranging effects. The most common visible features associated with Marfan syndrome include a long, lean body with a relatively short torso, long arms, long, thin fingers, chest wall abnormalities and flat feet with hammertoes. The most significant features, though, occur inside the body and include abnormalities in the heart, blood vessels, bones, joints and eyes. The NMF notes that Marfan syndrome does not affect a person's intelligence. The foundation estimates that approximately one in 5,000 people have Marfan syndrome. Men and women of all races and ethnicities are equally affected.
Sickle Cell Anemia
The National Heart Lung and Blood Institute—a division of the National Institutes of Health—states that sickle cell anemia is a serious genetic blood disorder in which the body produces sickle-shaped or C-shaped red blood cells. In normal, healthy individuals, red blood cells are disc-shaped and pass easily throughout the body's blood vessels. Red blood cells contain an iron-rich protein called hemoglobin that gives the blood its distinct red color and carries oxygen from the lungs to the body's cells. Hemoglobin abnormalities cause the sickling of red blood cells in people with sickle cell anemia, and sickle-shaped cells, which are stiff and sticky, clump together and are unable to pass easily through the blood vessels, often getting stuck. Any disruption in circulation due to blood vessel blockage can cause pain, discomfort, infections and even organ damage.
According to the National Tay-Sachs & Allied Diseases Association or NTSAD, Tay-Sachs disease is a progressive neurological genetic disorder that manifests in one of three forms—Classic Infantile, Juvenile or Late Onset. NTSAD notes that Tay-Sachs disease is caused either by the absence or insufficient amounts of the enzyme Hexosaminidase A in the body. Absent or insufficient Hex-A allows the lipid GM2 ganglioside to accumulate in cells, especially in the brain's nerve cells. The progressive, unchecked accumulation of GM2 gangliosides damages the brain's nerve cells. The Classic Infantile version of Tay-Sachs disease begins early in pregnancy, but symptoms do not appear until several months after the child is born. By the age of three or four, notes the NTSAD, the damage to the nervous system reaches a point where life can no longer be supported.