The 17 March 2005 issue of Nature (Vol. 434, No. 7031, pp 325-337 and pp. 400-404) reveals the genetic secrets of one of the most intriguing of human chromosomes: the X chromosome.
Female mammals carry two X chromosomes whereas males carry an X and a Y. This means that disease-causing genes on the X chromosome, including those causing haemophilia and X-linked muscular dystrophy, mainly cause problems in males who possess only a single gene copy. To ensure that females don't get a double dose of X chromosome genes, one copy is randomly silenced in each cell.
Mark Ross and his colleagues determined the sequence of over 99% of the gene-containing region of the X chromosome. The code reveals how the X and Y chromosomes evolved from a pair of regular chromosomes some 300 million years ago. Among other discoveries, the team predicts that nearly 10% of the 1,098 genes on the X chromosome are in a class that is upregulated in testicular and other cancers, and that a particular type of repetitive sequence takes up one-third of the entire chromosome and may to help silence the X chromosome's genes.
In a second paper that surveys X-chromosome-inactivated genes in more detail, Laura Carrel and Huntington Willard show that 75% of genes are silent all the time, about 15% escape inactivation and the remaining 10% are inactive on some X chromosomes but not others. This suggests that females differ widely in their pattern of gene activity, something that was previously unsuspected.
Mark Ross (Sanger Institute, Hinxton, Cambridgeshire, UK) Paper 
Tel: +44 1223 494839; E-mail: email@example.com
Laura Carrel (Penn State College of Medicine, Hershey, PA, USA) Paper 
Tel: +1 717 531 5419; E-mail: firstname.lastname@example.org
Huntington F. Willard (Duke University, Durham, NC, USA) Paper 
Tel: +1 919 668 4477, E-mail: email@example.com
Chris Gunter (Senior Editor, Nature, Washington, DC, USA) News and Views author
(C) Nature press release.
Message posted by: Trevor M. D'Souza
Bookmark and Share this page (what is this?)
Social bookmarking allows users to save and categorise a personal collection of bookmarks and share them with others. This is different to using your own browser bookmarks which are available using the menus within your web browser.
Use the links below to share this article on the social bookmarking site of your choice.
Read more about social bookmarking at Wikipedia - Social Bookmarking