Scientists crack puzzle of half-male/half-female chickens

A curious phenomenon that is seen in chickens, where one half of the bird appears female, and the other half male, has recently been solved by Edinburgh scientists. Previously there has been no explanation for the occurrence of these gynandromorphs; but now it appears that these are chimaeras composed of a mixture of male and female cells that retain their sex identity.These findings contrast with the mechanisms that were previously thought to govern the sexual development of all vertebrates. The traditional view is that male or female characteristics result from the production of hormones in the ovaries or testis. This research suggests that an alternate mechanism occurs in birds, in which basic differences between male and female cells control the development of sexual traits.This work, which is published in the journal Nature, not only sheds light on the process of sexual development in birds, but may also improve sexing assays used during poultry production and be relevant for understanding differences in behaviour and disease susceptibility between males and females.Dr Michael Clinton, who led the study, believes that we should now reassess how sexual development occurs in other organisms.