Segregation analysis on five samples of families with Hunter's syndrome (158 cases overall) shows that the mutant aliele segregates in agreement with Mendelian expectations for an X linked recessive disease, but the proportion of sporadic cases is significantly lower than expected under mutationselection equilibrium. Heterogeneity among the samples is apparent, but it is caused entirely by a sample of Ashkenazi families, whose segregation pattern has previously been interpreted as supporting the hypothesis of prenatal selection in favour of the pathological aliele. Conversely, our joint analysis of the five samples by a maximum likelihood approach does not suggest segregation distortion. Possible reasons for the apparent lack of sporadic cases include the effect of ascertainment bias.

The present study of 977 cystic fibrosis (CF) patients showed a bimodal birth distribution with peaks in April to July and October to January. After adjustment to the monthly variation of the birth rate of all liveborn children there was no significant deviation from the expected distribution. The 387 phenylketonuria (PKU) patients showed no seasonal birth variation.

The procedure for the detection of Hunter carriers suggested by Tønnesen et al. (1982) was checked in different mixtures of normal and Hunter cells as well as by examination of five obligate and five potential Hunter carriers. In the presence of fructose 1-phosphate there was a strict correlation between the proportion of mutant cells in the fibroblast culture and sulphate accumulation, both in artificial cell mixtures and in native cell cultures of Hunter carriers. In all obligate heterozygotes studied, sulphate incorporation was increased by a factor of two. The new technique seems to be suitable for carrier diagnosis. Its limitations are discussed.

In a large German family with Emery-Dreifuss muscular dystrophy (EDMD) linkage analysis was performed using the factor IX gene (F9), the factor VIII :C gene (F8), the anonymous DNA probe DXS52, and DXS15 as markers. Tight linkage was found between the EDMD locus and the F8 probe (Z_max = 1.19; Θ_max = 0.00), DXS15 (Z_max = 1.75; Θ_max = 0.00) and DXS52 (Z_max = 2.26; Θ_max = 0.00). Weak linkage was found to F9 (Z_max = 0.02; Θ_max = 0.43). The data from the literature and our results suggest that the gene locus of EDMD is close to F8 (confidence interval Θ = 0–0.07). The new linkage data are useful for carrier detection and diagnosis of EDMD patients before onset of major clinical signs.

SummaryIduronate‐2‐sulphatase was characterized kinetically in MPS II fibroblasts.