The sample set contains 98 Coriell samples (https://catalog.coriell.org) from 64 families with a variety of repeat expansions associated with dentatorubral-pallidoluysian atrophy (DRPLA, ATN1 gene), fragile X Syndrome (FXS, FMR1 gene), Friedreich's ataxia (FRDA, FXN gene), Huntington's disease (HD, HTT gene), myotonic dystrophy type 1 (DM1, DMPK gene), spinocerebellar ataxia type 1 (SCA1, ATXN1 gene), spinocerebellar ataxia type 3 (SCA3, ATXN3 gene), and spinal and bulbar muscular atrophy (SBMA, AR gene). This evidence concerns the gene DMPK and spinocerebellar ataxia type 1.