INTERMEDIATE INHERITANCE OF TOURETTE SYNDROME, ASSUMING ASSORTATIVE MATING

Segregation analysis incorporating assortative mating was used to test for major locus inheritance of Tourette syndrome in a single large pe digree containing 182 members. The analysis provided evidence of a maj or locus with an intermediate inheritance pattern for which the penetr ance was estimated from the data as 28% in heterozygotes and 98%-99% i n homozygotes. A significant assortative mating correlation was estima ted from the data as 70%-79%. In contrast, when assortative mating was not included in the model, intermediate inheritance was not inferred. If, in addition, constancy of the allele frequencies across generatio ns was not assumed, Mendelian transmission was rejected. Each subject, affected or unaffected, was assigned a score reflecting the presence and severity of symptoms. Higher mean scores in affected homozygotes t han in affected heterozygotes suggested greater severity in homozygote s: genotype information was obtained from genotype probabilities compu ted assuming intermediate inheritance.