Blood ring: an early embryonic lethal condition in chickens

Blood ring describes a lethal embryonic condition in chickens that is expressed between 48 and 66 h of incubation. The condition is characterized by the presence of uncoalesced blood islands, the absence of vitelline arteries, and a sinus terminalis engorged with erythrocytes. The disorder is inherited as an autosomal recessive trait. The recessive gene has been detected in three commercial populations of chickens with estimated gene frequencies ranging from 0.08 to 0.16. Attempts to identify the mechanism for the blood ring gene's expression have so far been unsuccessful. The gene symbol blr is proposed for the recessive gene.