Genetics 101: in search of a cure

A look at genetic testing’s benefits and possible personalized treatments . . .

Researchers around the world are focusing on gene mapping and DNA sequencing with the hope that personal genomics (the study of an individual’s genetic makeup) will help in the determination of personalized medical treatments.

Genetic testing examines your DNA, the chemical database that carries “instructions” for your body’s functioning, and looks for changes in your genes that may account for illness or disease.

Typical genetic tests include newborn screenings, carrier testing (identifies people who carry a gene for a disease and their likelihood of passing it on to their children), pre-symptomatic testing for genetic diseases in adults with a family history (determines one’s risk for developing that condition), and diagnostic testing in a person who has disease symptoms (will confirm if the individual has a suspected disease).

Most genetic tests are done by either a blood sample or a swab of the inside of the cheek. Tests are available in most hospitals, and results usually take three to four weeks.

The results are not always straightforward, and a person’s medical history, family history and type of genetic test must be taken into account. No matter the result, the goal remains the same: to empower patients through knowledge and allow them to be proactive about their health.

Susan Locke, MD, is Healthnetwork Foundation’s Medical Director.

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Making sense of genetic testing

Dr. Charis Eng

by Dr. Charis Eng

We are made up of cells. I tell my patients a cell is like an egg with a yolk and white. The yolk is the nucleus of the cell or the command center. It holds the DNA and the genes.

There are 30,000 different genes in humans and they are like 30,000 encyclopedias. These genes or encyclopedias can be small with only one volume or very large with 80 volumes. For the cell and body to be well, all 30,000 encyclopedias have to be arranged in order, and read well without typographical or grammatical errors. When a bad typographical error occurs in one sentence of a volume of an encyclopedia, a mutation has occurred.

Mutations in different genes mean different risks of different diseases. So finding the affected gene allows for very accurate diagnoses and begins the process of personalizing health care. Once a family-specific mutation is uncovered, then we can look for that one specific typo in every single member of the patient’s family in the setting of genetic counseling. This is called predictive testing because it can predict which family member who has yet to develop a disease has a high likelihood of doing so.

It is important to keep in mind that genetic testing is only one small part of the entire genetics evaluation, which includes genetic counseling and risk assessment as well. Based on a patient’s history, physical exam and the family health history, a tentative list of genetic diagnoses is formed in the genetic professional’s mind. This tentative list guides which gene to offer testing (after all, there are 30,000 genes and we cannot and must not offer testing indiscriminately at this time).

Charis Eng, MD, PhD, is founding director of the Genomic Medicine Institute (GMI) at the Cleveland Clinic.