F8 duplication and breakpoint mapping in family A. (A) Genomic region spanning the F8 gene according to the University of California Santa Cruz Genome Browser structure. The sequencing coverage in member III:2 of family A is plotted at the bottom. The duplicated region of ∼23.4 kb at the 5′ end of the F8 transcript (NM_000132) is indicated. Note that the F8 gene is oriented from right to left in this scheme. (B) Comparison of the normal and duplicated alleles (oriented from left to right). The exact breakpoint of the duplication, where intron 1 of the upstream copy is joined to the promoter region of the downstream copy, is indicated in the sequencing chromatogram. The inset in the top right corner shows the 7-bp sequence of microhomology between intron 1 and promoter that might have mediated the duplication event.