A defect in a gene can cause inherited diseases. Genetic testing may look at a chemical in blood or urine that is known to be associated with a disease. Genetic testing may involve DNA testing . If a DNA defect is known to cause a disease, healthcare providers can look for it to make a diagnosis. Genetic testing also may involve chromosome analysis.
Chromosomes contain many genes.
Genetic testing is performed when a person has a pattern of physical features that suggests a specific diagnosis. Down syndrome or a cleft palate , for examples, are genetic defects. They can be observed and then confirmed through genetic testing. The decision about which genetic test to do is determined by the features observed. The test itself is based on what is known about the defect that causes the disease.