Genetic Testing

In 2003, scientists mapped the entire human genome, that is, identified the ~25,000 genes in our DNA that make people, people. This information has been catalogued, cross-referenced, and applied to the detection and understanding of human disease. Unlocking this genetic code, of sorts, has enabled researchers to study the genetic basis of hundreds of human diseases. Some diseases, like Huntingon’s disease and sickle cell anemia can be traced to a mutation in a single gene. If you have the precise mutation, you will acquire the disease. Other diseases, like schizophrenia, are not caused by a mutation in a single gene, but rather several genes are likely to blame (along with environmental factors). With this explosion of information, genetic testing has become available for many different human diseases. However, as we will see, simply being able to detect the presence of a gene does not always tell us about the disease.

 

 

 Genetic testing is available for a large number of human genes. It has been applied to the detection of genetic abnormalities in unborn babies (fetuses). In this case, a few cells are taken during an amniocentesis procedure in which a long thin needle is inserted through the abdomen into the womb. This genetic testing approach can be applied to screening embryos for Down’s syndrome, for example.

 

Genetic testing may be performed on couples who are considered having children together but want to know if their genes, when combined, will lead to a disease with a genetic abnormality. In this case, a blood sample is obtained from both prospective parents and screened for a battery of genetic diseases. This type of genetic testing is best conducted under the guidance of a genetic counselor, that is, a doctor that can help direct genetic testing, explain the results of those genetic tests, and help form a course of action or direct treatment (when possible).

 

When a patient has one or more relatives with a disease with a known genetic cause, genetic testing may be performed to determine if the patient also carries the genetic mutation. Increasingly, people that are simply curious about their genetic makeup, without an affected relative, are requesting genetic testing of this nature. Direct-to-consumer genetic testing or DTC genetic testing is a form of genetic testing in which the person obtains a swab from their cheek or has a phlebotomist draw their blood and then send it a private company for analysis. The DTC genetic testing does not need a physician’s prescription, but also, unfortunately, does not provide physician guidance. Sadly many DTC genetic testing kits provide a laundry list of information regarding genes and gene mutations without discussion about what the possible abnormalities could mean. Often genes are tested that have not been shown to cause a human disease. Patients are either left worried that they may have an inescapable genetic disease or, at the opposite extreme, think they do not need to enact lifestyle changes because they are free of genetic diseases. DTC genetic testing without the guidance of a physician is fraught with problems and should be done with great caution (if at all).

 

While the colloquial expression that many use when discussing genetic testing is that genetic testing determines if one “carries the gene,” in reality all humans carry a copy of all genes (unless they have a deletion mutation). Thus the results of genetic testing are actually determining whether a person carries the mutation or chromosomal abnormality associated with a particular disease. While this distinction may seem hypercritical, it is actually important if you are considering genetic testing, especially if you are using direct-to-consumer genetic testing.