By definition, genetic testing is carried out by healthcare
professionals to look for a known cause of a specific disease in
someone who already has the symptoms or signs of the disease.
Laboratory studies can determine whether someone has the
condition. Genetic testing is performed when a person has a
pattern of physical features that suggests a specific diagnosis.
Down syndrome and cleft palate, for examples, are genetic
disorders. 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 genetic defect that causes the disease.
If a disease caused by a biochemical marker is suspected, the
doctor will order a biochemical test. If the basic disorder is
known, the doctor will order a DNA test or chromosome analysis.
Relatives of people with genetic disease may be tested to search
for inherited patterns. Biochemical genetic testing usually is
done on blood, urine or othe