We next screened for copy-number variations at the HDC locus in the general population, investigating 21,142 chromosomes using three detection algorithms (Table S6 in the Supplementary Appendix). No deletions or amplifications disrupting the transcript were identified. However, the probe density in this region limited the detection of copy-number variations to a minimum size of approximately 15,000 base pairs. Review of the Database of Genomic Variants revealed no HDC deletions and a duplication, identified by means of a bacterial-artificial-chromosome array, in two reportedly phenotypically normal individuals.8
