Examples for overprinting of genes. Gene structures of four genes are shown, whereby the exons (boxes) are drawn to scale, while the introns (lines) are not to scale. Open boxes are non-coding, filled boxes represent the reading frames. Ancestral gene versions are yellow, derived ones are purple. The Figure is based on annotations and graphics from Ensembl, whereby only the relevant splice variants are shown. A: Reep6 (ENSMUST00000030237 and ENSMUST00000060501); B: Polr1d (ENSMUST00000154641 and ENSMUST00000114425); C: Hoxa9 (ENSMUST00000048680, ENSMUST00000110557 and ENSMUST00000050970).