The whole genome sequence assembly of the Red Jungle Fowl (Gallus gallus), the ancestor of domestic chickens, has been publicly available since March, 2004, when it was initially deposited into the GenBank database for use by researchers around the world (www.ncbi.nlm.nih.gov/genome/guide/chicken). Today, a plethora of informative studies that utilize this sequence to study vertebrate evolution are published online in Genome Research, concomitant with the publication of a paper describing the primary sequence and comparative analysis in Nature (www.nature.com).
The chicken represents the most evolutionarily distant warm-blooded vertebrate relative to humans to have its entire genome sequenced. Until now, the organism closest to mammals whose genome had been sequenced was the pufferfish (Fugu rubripes), which shared a common ancestor with mammals approximately 400 million years ago. In contrast, only 300 million years have passed since the divergence of birds and mammals.
This new chicken sequence, representing a clade of at least 9,600 avian species, helps to fill the evolutionary gap between teleost fish and mammals.
An unusual genomic organization
A remarkable characteristic of avian genomes is the large variability in the size of their chromosomes. In addition to a pair of sex chromosomes (Z and W), chickens have 38 pairs of autosomes, which are classified into three sub-categories: macro-, intermediate, and micro-chromosomes. In one of the Genome Research letters published today, Hans Ellegren
Contact: Maria A. Smit
Cold Spring Harbor Laboratory