Confirmation of linkage of the loci for myotonic dystrophy and ABH secretion.

Mohr (1954) found hints that the locus of myotonic dystrophy belongs to the Secretor:Lutheran (Se: Lu) linkage group established by Mohr (1951). Despite their potential relevance for genetic counselling, these hints did not lead to further studies for reasons which may have revolved around the difficulties in phenotypic and genotypic categorization for the secretor and dystrophy loci. There may also have been some caution from an awareness of some limitations of the statistical procedures available at that time. A reappraisal of the dystrophy linkage data by Renwick and Bolling (1971) arose from a routine Bayesian analysis of Mohr's data undertaken in 1968 as part of their comprehensive analysis of available linkage data. Using computer help, they assessed the linkage relationships between the three loci jointly and obtained the posterior probability that all were syntenic (on the same chromosome). This probability was 0 93. Plans were made to collect further data and were stimulated by two further developments. One was the revival of interest (Renwick, 1969) in the indirect technique of prenatal diagnosis using a linkage relationship (Edwards, 1956). The other was the improvement in methods for early recognition of heterozygotes for the dystrophy allele. A linkage study is here reported in which a re-investigation of many of the pedigrees that had been studied for that purpose by Bundey, Carter, and Soothill (1970) increases the probability that the three loci, Dm, Se, Lu, are on the same chromosome pair (syntenic). A preliminary report has already appeared (Renwick et al, 1971).