The chicken fits the usual criteria of a model organism with it being cost effective, easily manipulated genetics, and a fast reproductive cycle. However chickens have an extra trait due to it being a member of the avian species, the ability to lay eggs. The egg allows scientists to conduct experiments during the embryo phase of the unborn chick without harming the mother. The egg shell can also be removed without damaging the chick embryo inside. The chicken embryo can be utilized to further understand the embryo stages of other animals with fewer ethical concerns. The chicken egg has been mainly used to create vaccines by growing and inactivating bacteria within the fertilized embryos while some of the chicken eggs have been used to research caner. Recently, after obtaining a genomic sequence of a chicken, it was observed that there are some functional proteins that are similar between chickens and humans. Researchers now believe that chickens could be used to study the non-coding regions in mammals.
I believe it is amazing that the chicken genome could give humans more information of the mammalian genetics. I didn't expect that chickens and humans could be so similar, but this also allows us to study mammalian genetics with lower ethical concerns. The egg makes it so that the mother hen isn't harmed during research, compared to a mouse carrying an unborn that is used for the same study. The study of the chicken genome could also give insight in how to better prevent more outbreaks of diseases within the domesticated chickens.