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.
Besides genes that determine sex, sex chromosomes carry many genes for traits unrelated to sex. X-linked gene is any gene located on the X chromosome that are missing on the Y chromosome. X-linked alleles are designated as superscripts to X chromosome. Newly discovered mutant male fruit fly had white eyes.