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.
Genes on the sex chromosomes are said to be sex linked. In the XY sex determination system of mammals, the X chromosomes carry a full set of genes, but the Y chromosomes carry few genes. Alleles or genes which are not sex-linked are called autosomal.