1 Colored Egg Layer Chickens. The Araucana is a pure breed of chicken originating in Chile. 2  Ameraucana chickens were developed in the 1970âs in the United States from Araucanas. They were developed as a practical barnyard fowl that laid pastel shelled eggs, but without some of the limiting genetic factors related to rumplessness and tufts.
sex chromosome. a chromosome, differing in shape or function from other chromosomes, that determines the sex of an individual.
Sex chromosome aneuploidy: an abnormal number of either the X or Y chromosome exists resulting in neither the classical XY male nor XX female. Mechanisms are the same as those in autosomal aneuploidy. Example: 45,XO = Turner syndrome.