Table 2

Frequencies of SMN1 copies per allele for each ethnic group

Ashkenazi Jewish0.01210.90720.08250.0002
African American0.00770.71880.26910.0001
  • *1D = disease allele (not caused by exon 7 deletions—for example, point mutations) as described by and based on frequency in SMA patients by Wirth et al (1999).11 De-novo mutations have also been described in spinal muscular atrophy (SMA) patients; however, their frequency is sufficiently low (∼2%) such that their inclusion in the calculations causes no change to these results at the level of precision used here.21