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Chicken, the First White Meat, Has Its Genome Analyzed

NEW YORK, Dec. 8 (GenomeWeb News) - An analysis of the chicken genome has been published in this week's Nature, revealing, among other findings, that roughly 60 percent of the protein-coding genes in the chicken genome have counterparts in the human genome.


The sequence of the red jungle fowl Gallus gallus, deciphered by the International Chicken Genome Sequencing Consortium, will enable researchers to compare similarities and differences between humans and the chicken, which has evolved separately from mammalian genomes for 310 million years. The sequence is also expected to provide information for researchers studying evolution, developmental and molecular biology, and agriculture.


The chicken is the first livestock or bird species to have its genome sequenced -- and is the most evolutionarily distant warm-blooded vertebrate, relative to humans, to have its entire genome sequenced.


The ICGSC, a collection of more than 170 researchers from 49 different institutes, sequenced approximately 1 billion base pairs in the genome of G. gallus, the wild ancestor of domestic poultry.


Researchers who analyzed the sequence discovered several immune-related genes previously thought to occur only in mammals. They also found long blocks of both the chicken and human genomes that contain genes that share the same chromosomal position, despite the relatively long evolutionary distance between the two species.


The researchers also noted that independent evolution of mammals and birds may be due to the expansion and contraction of gene families. They also found that the chicken appears to be the only vertebrate species whose genome has been sequenced to lose more genes than it gained during the evolutionary process.


Comparing the chicken and human genomes, the scientists found that at least 70 megabases of sequence are highly likely to be functional in both species, and that many of the chicken-human aligned, non-coding sequences occur far from genes, frequently in clusters that appear to be under selection for functions that are not yet understood.


In addition to the paper in Nature, the journal Genome Research has published several papers online today, which will appear in its January print issue, comparing the sequence of the chicken genome with other species, providing insight into aspects of vertebrate evolution.


In one of the studies published in Genome Research, Robert Ivarie, a professor of genetics at the University of Georgia, reports that although there are 78 chicken chromosomes, they contain only about one-third of the amount of DNA found in mammalian genomes. Scientists speculate that the smaller genome of the chicken is due to its lack of repetitive DNA elements: About 15 percent of the chicken genome contains repetitive DNA motifs, compared to 50 percent redundant sequences in mammalian genomes.


The draft of the chicken sequence has been publicly available since March 2004. The project was funded through $13 million in grants from the National Institutes of Health and was completed at the WashingtonUniversityGenomeSequencingCenter in St. Louis, Mo.

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