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. 2002 Feb;4(1):11–29. doi: 10.1016/S1525-1578(10)60676-9

Figure 2.

Figure 2.

Use of internal restriction digestion control to avoid misdiagnosis. The PCR reaction generates a 204-bp product from the LAMA3 gene and a 461-bp product from the LAMB3 gene (which is used as an internal control). Digestion with Dde I cleaves the LAMB3 product into fragment sizes of 273, 103, and 85 bp (Bc) and cleaves only the LAMA3 allele that contains the R650X mutation (into fragment sizes 138 bp and 66 bp). M, Marker 1-kb DNA ladder (φX174 DNA/Hae III marker, Promega Corporation). Lanes 1–10: Single lymphocytes heterozygous for R650X mutation in LAMA3 gene. Au and Bu, uncut LAMA3 and LAMB3 PCR products, respectively. Allele dropout (*) is apparent in lanes 2, 7 and 8. The internal digestion control prevents an affected cell being misdiagnosed as unaffected (as a consequence of failed Dde I digestion) since the LAMB3 product remains undigested (Bu) at 461 bp.