NEW YORK, March 17 (GenomeWeb News) - An international research consortium has published the gene sequence of the human X chromosome in this week's Nature.
This sequence joins detailed annotations and analyses already published for chromosomes 5, 6, 7, 9, 10, 13, 14, 19, 20, 21, 22, and Y as part of the International Human Genome Project.
Lead researcher Mark Ross of the Wellcome Trust Sanger Institute and researchers from Baylor College of Medicine; Washington University School of Medicine, St. Louis; the Max Planck Institute for Molecular Genetics; the Institute of Molecular Biotechnology; and Applied Biosystems conducted the analysis that has determined 99.3 percent of the X chromosome's euchromatic sequence, and the existence of 1,098 genes, including 399 "new" genes and 99 cancer-testis antigen genes.
The research team also compared the chromosome to the genome sequences of a variety of other organisms, including dog, rat, mouse, and chicken. They found that the gene order of the human and dog X chromosomes were virtually identical.
By comparing gene order in the human and rodent sequences, the researchers found several segments had reshuffled in the rodent lineage, and a 9-million-base-pair region appears to have been deleted from the rodent chromosome after humans and rodents diverged from their common ancestor.
In the comparison of the human X chromosome to the sequence of the chicken, the researchers found that most of the genes on the short arm of the human X are found on chicken chromosome 1, and most of the genes on the long arm of the human X are found on chicken chromosome 4. These findings support the idea that mammalian X and Y chromosomes evolved from an "ordinary" ancestral pair of identical chromosomes.