Sex-ration in wild and domestic birds

Abstract

Sex chromosomes determine the sex of embryos in all superior vertebrates including birds. Based on the Mendel laws of segregation of characters, progeny sex ratio in a given population is theoretically equilibrated. However,, examples of unbalanced sex ratio have already been described both in wild and domesticated avian species, suggesting that females in these species may influence the distribution of sex chromosomes, or favour embryo development of one rather than the other sex. Here, we review the circumstances under which female-induced control of genetic sex allocation to the progeny may occur. While a direct demonstration of this phenomenon remains to be established, accessing the underlying mechanisms involved in this type of regulation would provide access to the poultry specialist’s old dream of producing females only in layer type chickens and males only in meat-type chickens and mule ducks…