The bird is one of the world’s most diverse species in the kingdom of Animalia for its variety of color and patterning. Now researchers have uncovered which genetical mechanisms are responsible for such patterns. A group of Swedish and French researchers made a research on the Coucou de Rennes chicken which is known for its sex-linked barring pattern.

In the journal of PLOS Genetics researchers described that two independent mutations affect the function of Cyclin Dependent Kinase Inhibitor 2A(CDKN2A). This is a protein coded tumor suppressor gene in chickens which is associated with human melanoma. Over the past few decades, several types of research have been made in pigmentation biology to identify the pigmentation controlling gene in mammals and birds, but how color patterns are genetically controlled, is still a challenge.

A new study reveals that barring patterns in French breed Coucou de Rennes are related to same plumage color present in common cuckoos(Cuculus canorus). all type of birds including chickens have two types of chromosomes: Male has ZZ and female has ZW chromosomes. The Z chromosome which is common in both male and female carries the locus of sex-linked barrings.

Lead researcher Leif Andersson from Swedish University of Agricultural Sciences and Texas A&M University said in his statement,“We are sure that both mutations contribute to the sex-linked barring pattern because we have also studied chicken that only carries the regulatory mutation and they show a very pale plumage with only weak dark stripes”. According to EurekAlert, two independent mutations act together to form sex-linked barrings.

First one is known as the regulatory mutation which regulates the expression of CDKN2A and the second one changes the protein sequences. In contrast, sex-linked barring in chicken is just the opposite effect of the same mutation which causes melanoma in humans. During the development of each feather, CDKN2A plays an active role in the cyclic deficit of pigmentation that causes white stripes.

On the other side, White Leghorn that is one of the most popular chicken breeds for egg and meat production has the same mutations in their tumor suppressor gene. But, sex-linked barring is not to be seen in their feathers because their dominant white color eliminates all the pigment production and masks the effect of sex-linked barring.