ANALYSIS OF THE VIQ SCORES OF FAMILIES OF 3 OR MORE ORKNEY BROTHERS

Classification of the boys in 48 families of three or more brothers ac cording to their Moray House Test (VIQ) scores awarded at age 11 +/- 1 1/2 years in 1947-75 confirms the postulated existence of a total of n ine male phenotypes for this X-linked trait in the score range <70 to 140 points. The phenotypic means lie close to the sequence 69(8)133. R ecombination is shown to occur. An additive effect of three alleles at each of two X-chromosome loci is the most likely simple scheme. An it erative approach matching the observed mixtures of proposed genotypes in the families with probabilities for variable levels of homozygosity , non-crossover/crossover heterozygosity, and maternal meiotic recombi nation yields a best goodness of fit where this last is 20%.