Schematic of F8 intron 22 and intron 1 inversion mutations. (A-C) Light gray rectangles indicate exons 1 to 22, dark gray rectangles indicate exons 23 to 26, and black rectangles indicate the homologous sequences int22h1, int22h2, and int22h3, which are abbreviated h1, h2, and h3, respectively. Introns and extragenic DNA are indicated by black lines. Exons and introns are not drawn to scale. (A) The normal F8 gene. (B) Homologous recombination between int22h1 and either int22h2 or int22h3 separates exons 1 to 22 from exons 23 to 26. (C) The inverted F8 gene. (D-F) Light gray rectangles indicate exons 1 to 26, dark gray rectangles indicate the facultative exons F1 and F2 and VBP1 and BRCC3 genes, and black rectangles indicate the homologous sequences int1h1 and int1h2. Introns and extragenic DNA are indicated by black lines.