Chromosomes make up the building blocks of our bodies. Each human inherits 23 chromosomes from his or her mother and 23 chromosomes from his or her father, for a total of 46. Most often the process is flawless and produces a healthy baby.
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However, there are certain times when children inherit abnormal genes from their parents -- and even generations prior -- that result in debilitating and often fatal diseases. Our DNA also contains "instructions" every part of our body needs to develop, and in rare cases, the "message" can become distorted, which can also cause abnormalities and defects.
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Sickle cell disease is an inherited blood disorder in which red blood cells contain mostly hemoglobin S rather than hemoglobin A. This image shows a microscopic view of sickle cells, which become misshapen (crescent-shaped) and have difficulty passing through the blood vessels.
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Duchenne muscular dystrophy (DMD) is just one of nine forms of muscular dystrophy that begins to attack children between the ages of 2 and 6. Patients who suffer from DMD are missing the protein dystrophin, which helps keep muscle cells intact. This slide shows the cross section of the calf muscle of a patient who died of DMD. The muscle fiber has been replaced almost entirely by body fat.
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Cystic fibrosis, which affects approximately 30,000 children and adults in the United States, claimed the life of Emily Haager, seen here on July 18, 2009, speaking as ambassador for the Second Annual Pipeline to a Cure for the Cystic Fibrosis Foundation in Huntington Beach, Calif. She lost her battle May 1, 2010, at just 27 after living as an adult with CF, a genetic disease that causes mucus buildup in the organs, particularly the lungs and pancreas.
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One in 25,000 babies is born with Phenylketonuria (PKU) and cannot process the part of protein known as phenylalanine, which is found in most foods. It's treatable with a special diet, although if left untreated can lead to mental retardation. PKU occurs in all ethnic groups, but is most common among descendants of Native Americans and Northern Europeans.
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Cleft lips or cleft palates (or both) are common genetic disorders that can be caused by a number of genetic mutations. Here, a child with a cleft lip awaits surgery at the Rotaplast Clinic in Maracaibo, Venezuela. Rotaplast International is a San Francisco-based organization that sends medical teams to poor countries to provide free reconstructive surgery to children with cleft lips and palates.
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Progeria (also known as Hutchinson-Gilford progeria syndrome), however, is an extremely rare genetic disease -- it reportedly affects only 1 in 4 to 8 million newborns worldwide -- caused by a mutation in the gene LMNA. Symptoms cause characteristics of aging, like high blood pressure and heart failure. Most children live about 13 years and typically die of heart disease.
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Strides are finally being made in the treatment of progeria. Farnesyltransferase inhibitors (FTIs), originally developed for cancer treatment, have shown to reverse the nuclear structure abnormalities seen in the cells of children with progeria. Shown here are untreated cells from a child with progeria (left) compared to similar cells treated with FTIs.
Image Credit: National Human Genome Research Institute
Of course children aren't the only ones who live with genetic diseases. This shows the brain scan of an adult suffering from Alzheimer's disease. Apolipoprotein E-e4 (APOE-e4) is the gene scientists have determined puts us at risk for Alzheimer's. We inherit a copy of some form of APOE (APOE-e2, e3 or e4) from each parent. Those who receive one APOE-e4 have an increased risk of Alzheimer's; those who inherit two APOE-e4 genes have an even higher risk, but not a guarantee, of Alzheimer's.
Image Credit: National Institute on Aging
This shows the scan of a normal brain. Notice how much more activity it shows. Aside from the APOE-e4 risk gene, deterministic genes that are known to absolutely cause "familial Alzheimer's disease" have also been discovered in a few hundred families worldwide. Genetic tests are available for both.
Image Credit: National Institute on Aging
TLC's Amy and Matt Roloff are probably the country's best-known little people. Amy was born with achondroplasia dwarfism and Matt with the rarer diastrophic dysplasia, despite the fact that both have parents of average height. They have four children of their own, including Zach, who was also born with achondroplasia.
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Melanoma is the most dangerous form of skin cancer, and everyone is at some risk. But about 10 percent of patients diagnosed have a family history of the disease. Having a first-degree relative like a mother, father or sibling diagnosed with melanoma increases your risk by at least 50 percent and you are considered part of a melanoma-prone family.
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There are many factors that determine which of us are most at risk for coronary artery disease. Some key factors, like age, gender and genetics, we cannot control. Remember the gene apolipoprotein E-e4 (APOE-e4) that increases our risk of Alzheimer's? Well, its presence raises our risk for heart disease, as well, because it affects cholesterol levels, especially those that cause heart disease. This image shows a coronary artery more than 50 percent blocked by plaque.
Image Credit: National Human Genome Research Institute
In many cases, depression seems to have a direct relation to genetics. In fact, studies have found that children are at higher risk of depression if one parent has a history of depression, and that risk is even higher if major depression affects both parents.
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As with many types of cancer, breast cancer may have a genetic link. According to the American Cancer Society, about five to 10 percent of cancer cases are inherited when an abnormal gene is passed on from generation to generation. Mammograms are one method of diagnosing breast cancer early, which is key to successful treatment.
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Genetics can play a strong role in diabetes, as well. Type 2 diabetes in particular often has its roots in family history, especially since bad eating habits and obesity also tend to run in families. With type 1 diabetes, a child needs to inherit risk factors from both parents.
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Amyotrophic lateral sclerosis (ALS) is often called Lou Gehrig's disease after Lou Gehrig, who played baseball for the New York Yankees and was diagnosed with the disease in the 1930s. ALS, which damages motor neurons in the spinal cord and brain, is hereditary in up to 10 percent of cases.
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Woody Guthrie, a popular American folk singer and musician, is shown here with his companion and former wife, Marjorie Guthrie, and their son, Arlo Guthrie, in 1966. Guthrie had Huntington's disease, and near the end of his life, he was only able to communicate by pointing to signs. Huntington's, which most often appears in adulthood, is usually inherited from one parent who had the altered gene that causes the disease.
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Champion boxer Muhammad Ali and actor Michael J. Fox both have the degenerative nerve condition known as Parkinson's disease, which is a progressive disorder of the nervous system. In about 15 percent of cases, people with Parkinson's have a family history of the disease, but the inheritance pattern is still largely a mystery to researchers.
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Tourette's syndrome, a neurological disorder characterized by involuntary and sudden movements or vocal tics, has a strong pattern of inheritance that involves a variety of genes. Here, Dr. Mortan Doran, a surgeon who suffers from Tourette's, constantly touches his sons' heads and shoulders in a very specific rhythm, which is made visible by small lights attached to his fingers.
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Multiple sclerosis (MS) is a degenerative disease of the nervous system that affects women more often than men. One study showed that relatives of MS patients may be up to seven times more likely to be diagnosed with the disease than those with no family history of MS. Actress Annette Funicello announced her MS diagnosis in 1992.
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