Chicken genome sequenced

9/12/04. By Wellcome Trust Sanger Institute

Genome analysis of the red jungle fowl, a wild ancestor of the domestic chicken, is completed by an international consortium.

The first detailed analysis of the chicken genome has identified a chicken counterpart to an important human immune system protein, revised scientists' assessment of the chicken's sense of smell, and suggested that the chicken, long used to study gene activity in the earliest stages of life, may provide a good model for studying changes in DNA linked to aging and death.

Other findings from the analysis, reported in the 9 December issue of the journal Nature by the International Chicken Genome Sequencing Consortium, include the identification of genes that affirm the chicken's value as a model for study of developmental disorders like cleft palate and diseases like muscular dystrophy. The Wellcome Trust Sanger Institute contributed sequence and analysis to the Consortium.

Researchers completed and made available the genetic sequence of the red jungle fowl - a wild ancestor of the domestic chicken whose scientific name is Gallus gallus - in March 2004. The genome provides several firsts: it is the first bird, the first agricultural animal, and the first descendant of the dinosaurs to have its genome sequenced.

The International Chicken Genome Sequencing Consortium is directed by Richard K Wilson, PhD, Director of the Genome Sequencing Center at Washington University School of Medicine in St. Louis.

Wilson and other project leaders predict that the chicken genome will help biomedical researchers seeking to better understand the human genome in order to improve diagnosis and treatment of human disease. Another paper appearing in 9 December issue of Nature found relatively little genetic difference between Gallus gallus and domesticated chicken breeds, highlighting the genome's potential to aid agricultural scientists trying to improve the chicken as a nutritional resource and to limit the spread of avian flu viruses.

Scientists found the chicken genome has about the same number of genes as the human genome: 20 000-23 000 compared with the human genome's estimated 20 000-25 000 genes. However, those genes are contained in only 1 billion DNA base pairs, a mere third of human DNA's 2.8 billion base pairs. A part of what’s missing is some of the 'junk' DNA - the recognisable repetitive content of the chicken genome is only about 10 per cent as compared to about 50 per cent for humans.

Scientists identified a chicken gene for interleukin 26, an important immune response protein only previously seen in humans. Researchers hope that further study of the chicken's immune system will lead to the development of better ways to control the spread of viruses, such as the bird flu in Asia. These viruses sometimes jump across species and infect humans.

The chicken has traditionally been regarded as having a poor sense of smell, but an assessment of the number of smell receptors in the chicken genome has scientists reconsidering. The total number of receptors doesn't put the chicken in the same league as olfactory champions like the dog or the mouse, but it may place the chicken's sense of smell on a par with the human sense of smell. However, a search for taste receptors turned up relatively few results, suggesting chickens have a poor sense of taste.

Based on their initial look at the chicken genome, scientists have suggested that they may need to alter the proposed starting point for as many as 2000 human genes. Their analysis showed that chickens and humans share about 60 per cent of their genes, as opposed to the approximately 88 per cent shared by humans and rodents.

The International Chicken Genome Sequencing Consortium includes scientists from China, Denmark, France, Germany, Japan, Poland, Singapore, Spain, Sweden, Switzerland, the United Kingdom and the United States.

Adapted from a press release by the Wellcome Trust Sanger Institute .

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Chicken genome sequenced

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