Bh (black at hatch) gene appears to cause whole-body hemorrhage in homozygous embryos of Japanese quail (Coturnix coturnix japonica).

Genotypes of early embryos obtained from mating Bh/+ quail were determined by chorio-allantoic membrane grafting of their thigh skin, and the development of the Bh homozygous embryos was examined histologically. The Bh homozygous embryos died at an early stage of development (after 7 to 10 days of incubation) with a very high incidence of whole-body hemorrhage (approximately 100%), but malformation of neural tubes was not always accompanied by Bh homozygosity. Degeneration of the liver was more frequently observed in homozygous embryos than in wild-type and heterozygous embryos. The results suggest that the Bh gene causes whole-body hemorrhage and subsequent death of homozygous embryos. In addition, our data indicate that Bh homozygotes would develop brown feathers on their skin if they were able to survive.