The study, published yesterday in the journal Proceedings of the National Academy of Sciences (PNAS), looked at how genes on sex-linked chromosomes are passed down generations and linked to fertility, using the specific example of the W chromosome in female chickens.

An international team of more than 70 researchers says it has found nine new genes on the X chromosome that, when knocked-out, lead to learning disabilities. The scientists said they studied nearly all X chromosome genes in 208 families with learning disabilities.

Independent research papers from Dr. Peter Becker (Munich, Germany) and Dr. Mitzi Kuroda (Boston, MA) in the October 1 issue of Genes & Development delineate the mechanism of X-chromosome dosage compensation in Drosophila.

CHICAGO - An international team of researchers announced Wednesday that they have cataloged all the genes on the female X chromosome, a technical feat expected to enable fresh insights into women's health as well as adding a genetic component to the debate over differences between the sexes.