SMN genes and assays to interrogate possible genotypes. Forward and reverse primers and probes shown 5′ to 3′ specific to the amplification of SMN1 are as follows: (Assay A forward: CTTGTGAAACAAAATGCTTTTTAACATCCAT, LNA reverse: ATTGTTTTACATTAACCTTTCAACTTTTT, LNA probe: Cy5/ GGTTTCAGACAA /3IAbRQSp) and (Assay B exon: forward CTTGTGAAACAAAATGCTTTTTAACATCCAT, Assay B exon reverse GAATGTGAGCACCTTCCTTCTTTTT, Assay B exon LNA probe Cy5/TTGTCTGAAACC/3IAbRQSp and Assay B intron forward TTGTGGAAAACAAATGTTTTTGAACA, Assay B intron reverse GTAGGGATGTAGATTAACCTTTTATCTAATAGTTT, and Assay B intron LNA probe HEX/CAACTTTTTAACATCT/3IABkFQ).