The Bal I and Msp I polymorphisms in the dopamine D3 receptor gene display, linkage disequilibrium with each other but no association with Tourette syndrome.

The D3-dopamine receptor gene, DRD3, has been considered as a candidate gene in several disorders in which the dopaminergic system has been implicated including Tourette syndrome and schizophrenia. The DRD3 studies to date have all used as the gene marker a Bal I polymerase chain reaction restriction fragment length polymorphism (PCR RFLP). There have been recent reports on a second marker, an Msp I PCR RFLP, that lies 40 kb downstream. We have typed a sample of 16 Tourette syndrome families with both markers and observed significant linkage disequilibrium between the two markers but no apparent association of either marker with Tourette syndrome.