A chromosome is a single DNA molecule that may contain different units of inheritance called genes, along with proteins that help to activate these genes under certain conditions.

Even though it is the presence or absence of the human Y chromosome that directs sex development, human females still need to determine how many X chromosomes they have in each cell. They do this to ensure that similar amounts of the proteins encoded on the X chromosomes are produced in each sex. Failure to properly count X chromosomes is lethal to embryos of mammals and flies. That's why biologists want to understand the process of "chromosome counting."

Early in his career, Erickson was part of the research team that identified the genes involved in counting Drosophilia sex chromosomes. Now, he and Avila have made another breakthrough, identifying a signaling pathway outside the cell that helps trigger a cascade of proteins to ensure embryos remain either male or female once their sex has been determined, as well as help in the chromosome-counting process and in regulating other crucial cell activities.

"This signaling process is not unique to embryonic sex differentiation, but occurs in hundreds of genes throughout the body, in flies and in higher animals, too," Avila says. "Our work sheds light on signal transmission in humans."

Erickson points out that flies have evolved along with humans and that the two species are "close."

Although he is quick to point out that the group's research has no short-term practical application, he believes down the road it has important implications for human health.

"Scientists have been trying to understand how the sex of mosquitoes is determined, with an eye to eradicating those which carry diseases," he says. "Our research on fruit flies may he
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Contact: Judith White
judith-white@tamu.edu
979-845-4645
Texas A&M University
27-Mar-2007