Fig. 3

Analysis of the BRCA1 Ex20dup transcript. A Sanger sequencing results of cloned cDNA fragments of Family 1 patient III:1 confirm the expression of an in-frame BRCA1 Ex20dup transcript. Black arrows in the upper panel indicate exon transitions. B PCR-amplification of cDNA retrieved from Family 2 patient IV:2 provides two products spanning from exon 15 to exon 21. A heterozygous single nucleotide polymorphism (rs1799966, underlined) located on exon 16 allows discrimination between the transcripts originating from the wild-type allele (approx. 700 bp) and the BRCA1 Ex20dup carrying allele (approx. 800 bp). The corresponding uncropped original gel image is shown in Additional file 1: Figure S3