Genetic basis of familial amyotrophic lateral sclerosis

To the Editor: Conneally has presented an informative discussion of the implications of the detection of markers for a major gene (May 16 issue).¹ The immediate stimulus was the report by Siddique et al. in the same issue of four DNA markers on the long arm of chromosome 4 that, in a subgroup of families, were linked to the familial form of amyotrophic lateral sclerosis.² In sharing with us some of the background of the study, Conneally points out that a simple but highly unusual step was critical to its success — the decision by two competing groups of investigators.