A genetic disorder is caused when an abnormality in the genetic framework of an individual is present. Genes are passed from parents to child. When a mutation of a gene occurs, it prevents it from developing normally. Some genetic disorders are inherited and others are a result of malformation of cells during development. There are four types of genetic diseases---single-gene diseases, multi-factorial diseases, chromosomal diseases and mitochondrial diseases.
Cystic Fibrosis
Cystic fibrosis, the most common fatal genetic disease in America, is a single-gene genetic disease. It requires the passing on by both parents of the defective gene responsible for the disease. This defect causes the development of mucous that clogs the lungs and negatively affects the pancreas. The symptom of salty-tasting skin is caused by the inability of the body to move sodium chloride in and out of cells. Children may inherit only one faulty gene and be a carrier, passing along the defective gene to their children.
Huntington's Disease
Huntington's disease, a single-gene genetic disease, affects the ability to talk, move and think. This inherited disorder is a result of a disease process that destroys cells in the brain. Huntington's disease is a certainty for everyone who inherits the mutated gene. Genetic testing for this incurable disease can determine if the mutated gene is present in the fetus or at any age.
Alzheimer's Disease
Alzheimer's disease (AD) is a multi-factorial genetic disease caused by mutations in multiple genes and environmental factors. Alzheimer's may be early onset, affecting people between the ages of 30 and 60, or it may be late onset, affecting individuals 60 years and older. Early-onset AD is rare, but only requires one of the mutated genes from a parent. Late-onset AD does not have the same genetic mutations as early-onset. Alzheimer's affects a person's thought processes, memory and language.
Breast Cancer
Breast cancer, a multi-factorial disease, may or may not be inherited. Two known genes associated with breast cancer are BRCA1 and BRCA2. Individuals with a mutated form of BRCA1 or BRCA2 are at a higher risk for developing breast cancer. Men and women can be affected or pass the mutation on to their children.
Down Syndrome
Down syndrome is a chromosomal abnormality caused by abnormal cell division of chromosome 21. Three abnormal divisions can occur---Trisomy 21, mosaic Down syndrome and translocation Down syndrome. The most common is Trisomy 21, an abnormality that occurs during sperm cell or egg cell development. Flattened facial features and a protruding tongue are common symptoms of Down syndrome.
Mitochondrial Diseases
Mitochondrial genetic abnormalities affect the energy-giving part of cells. The mitochondria produce the energy to keep the body functioning. A mitochondrial abnormality can shut down the energy supply for any cell. This shut-down can be multi-system or specific to a particular group or groups of cells. The effects on muscle and nerve cells include muscle weakness, hearing loss, heart irregularities, seizures, difficulty with balance and diabetes. Mitochondrial genetic diseases include Alpers disease, Complex IV deficiency, mitochondrial myopathy and lactic acidosis.
