Most of the genetic disorders that we know about are due to mutations in the sequence of the DNA that alter how the functions of genes. For example, in sickle cell anemia, changing an adenosine in the sequence of the β-globin gene to a thymine alters the property of the β-globin such that it causes red blood cells to sickle under low oxygen conditions.
For genetic diseases whose causes are known, there are
tests one can perform to check an individual's DNA for mutations that are indicative of these genetic disorders. These tests can inform potential parents of the likelihood of conceiving a child with a genetic disorder or can be performed on unborn children to inform parents of any genetic disorders their child may have. Although
gene therapy could be used in theory to correct these disorders, gene therapy remains an experimental technique, and there are currently no therapies approved to correct genetic disorders in people, although some lifestyle changes may lessen the effects of certain genetic disorders (e.g. see
phenylketonuria).
As DNA sequencing technology becomes cheaper, doctors may be able to diagnose genetic disorders by sequencing all of the DNA from an individual. These sequences may reveal mutations in genes that are not well studied that could cause potential genetic diseases. Predicting the effects of these mutations can be difficult, and this is an area we still need to study in order to realize the full potential of whole genome sequencing as a diagnostic tool.