Our goal is to map one or more Tourette Syndrome genes to an approximate site on one of the chromosomes. The approach we are following is the same as that being followed by several other laboratories: namely, to demonstrate, within affected families, coin heritance of the disease gene with a mapped, polymorphic DNA marker. Our new twist to the problem is to use a novel collection of DNA markers based on length polymorphisms within blocks of abundant dinucleotide repeat sequences. These markers are moderately to highly informative and are designed so that they can be typed efficiently using a powerful and sensitive new technique called the polymerase chain reaction. It is hoped that with this new approach, more DNA markers can be tested more rapidly than with conventional approaches, thereby increasing our chances of finding at least one marker located near a Tourette gene. With the assistance of Drs. P. Ahmann, R. LaPlant and B. Hiner, we have recently completed the analysis of one large Wisconsin Tourette family, and have begun work on several others. In addition, a collaboration has been initiated with Drs. B. Oostra, P. Heutink and B. van de Wetering at Erasmus University in Holland. DNA samples from the Dutch and Wisconsin Tourette families have been exchanged, thereby increasing substantially the number and size of the families available to us for mapping. With the generous support of TSA, we expect to make considerable progress on gene mapping within the coming year. James Weber, Ph.D. Marshfield Research Foundation, Marshfield, WI Award: $19,700 Tourette Association of America Inc. – Research Grant Award 1989