On Nov. 15, 1996, for the first time, scientists pinpointed the location of a gene they believe is responsible for some cases of Parkinson’s disease. Their discovery provided strong evidence that a genetic alteration is capable of causing the disease.

The impact of the current finding is to show that a single gene alteration can cause the disease. The next step will be to find and identify the specific gene involved, which is located somewhere within a region of DNA on the long arm of chromosome 4.

Learning the gene’s exact location and isolating it may eventually lead to genetic testing that will help early diagnosis and treatment. Learning what the gene is and how it works may help researchers design treatments for all forms of Parkinson’s disease – not only inherited cases, but also those with no familial link.

The gene mutation in this family is inherited in a dominant fashion, meaning that people who possess the mutation have a 50 percent chance of passing it on to their children. Only one parent must carry the mutation for the disease to appear in a couple’s offspring. The symptoms of familial Parkinson’s are identical to those in families with no history of the disease, except that the inherited form sometimes develops earlier in life.

The study, published in the November 15 issue of Science, sheds light on the mysterious origins of this devastating neurological disease that affects at least 500,000 Americans.