Figure 4: Mutation analysis in the girl with Bloom syndrome. Electropherogams from Sanger sequencing. A: DNA from peripheral blood reveals the heterozygous mutation c.1624delG in BLM exon 7 on the sense (upper panel) and antisense (lower panel) strand. B: The other heterozygous mutation in peripheral blood DNA is c.3415C>T in BLM exon 18 shown on the sense (upper panel) and antisense (lower panel) strand. C: DNA from a lymphoblastoid cell line retains the heterozygous mutation c.1624delG on both strands, but has lost the mutation c.3415C>T (sense and antisense strand, respectively), confirming somatic reversion.