Abstract: The underlying genetic defect of Huntington disease (HD) has been mapped to chromosomal band 4.sub.p 16.3. Refined localization using recombinant HD chromosome analysis and allelic association analyses have identified two distinct candidate regions. Using a cDNA hybrid selection procedure, .alpha.-adducin has been mapped to the proximal 2.2 Mb 4D gene candidate region within 20 kb of D4S95. Several clones have been mapped within the minimal region containing the HD gene. The clones GT 70 and GT 149 are particularly useful in detecting changes in this portion of the gene of HD patients.