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May 1995

Dopamine D2 Receptor and Tourette's Syndrome-Reply

Author Affiliations

Department of Psychiatry Veterans Affairs Medical Center 116A2 West Haven, CT 06516

Arch Neurol. 1995;52(5):442-443. doi:10.1001/archneur.1995.00540290019005

In reply  We appreciate Comings' observations and comments on our article,1 but we still cannot endorse his conclusions because the analyses he used are not suitable for the problem. As we noted in our original article, it is inappropriate to extract allele frequencies from family data for comparison to allele frequencies from sets of unrelated individuals. The reason for this is that allele frequencies within a family primarily represent those in the family's progenitors. This produces inflated sample sizes, when the whole family is considered, that can make small random fluctuations in allele frequency appear significant. This is the sort of comparison made by Comings.To understand this point, imagine that we are studying a genetic system with two alleles, such as the DRD2 Taq "A " system, with allele frequencies of 0.18 and 0.82. Assume that there is a nuclear family where both progenitors, ie, the father and mother,