Genetic diseases are caused by defects in genes, segments of DNA that govern specific characteristics in a person. Common genetic disorders such as cystic fibrosis or Huntington's disease aren't always inherited, but may occur as a spontaneous gene mutation. Common genetic disorders such as a tendency to have elevated cholesterol levels, one of the most common genetic disorders, or high blood pressure, may not be evident at birth. Some genetic disorders never become evident unless certain environmental factors interact with the gene.
Types
There are three common types of genetic disorders. Single gene or monogenic disorders occur when a single mutation occurs on a gene. As many as 1 in 200 newborns have a single gene genetic disorder, reports the website Genetic Diseases. Cystic fibrosis, sickle cell disease and Huntington's disease, all common genetic diseases, occur because of single gene defects, usually inherited but sometimes caused by spontaneous mutations. Mutlifactorial genetic diseases occur because of a complex interplay between several genes and environmental factors. Obesity, Alzheimer's disease, diabetes and some cancers occur due to multifactorial genetic issues. Chromosomal defects occur because of structural changes or other abnormalities on chromosomes which are made up of many genes. Down syndrome is the best known and most common chromosomal defect.
Causes
Genetic inheritance is classified as dominant or recessive. A dominant gene disease can occur in a child if only one parent has the gene, while recessive diseases occur only if both parents have the defective gene. Cystic fibrosis and Tay-Sachs disease are recessive diseases, while Huntington's disease occurs as a dominant gene disease. Common chromosomal defects like Down syndrome usually aren't inherited but occur because of abnormalities in the egg, sperm or embryo at conception.
Testing
Genetic testing is easier for common genetic defects than for more rare defects. Testing for most common genetic disease can be done prenatally through amniocentesis or chorionic villus sampling. As of 2010, genetic tests are available for around 1,000 genetic diseases, LabCorp states. Genetic screening can also be done on embryos created in the laboratory through in vitro fertilization, although the procedure is costly, or through simple blood or cell tests after birth.
Treatment
Common genetic disorders can't be cured by removing or modifying the defective gene or chromosome. While treatments can reduce symptoms, the diseases themselves can't be eliminated.
Considerations
Not everyone wants to know they have a genetic disease or to test their children for common genetic diseases during pregnancy. Being diagnosed with a genetic disease can impact getting health or life insurance, for example. Knowing that a person has a disease he can't do anything about may cause serious psychological damage in some cases.
