Scientists' understanding of how genetic material moves when cells divide has dramatically changed with a new finding that may be key to the study of genetic diseases. New evidence from the fruit fly suggests that the critical life process of cell division is more precisely controlled than previously believed. Genetic material is moved along its entire length by many tiny chemical "motors," according to an article published in the April 7 issue of the journal Cell by University of California, Davis, professor Scott Hawley, graduate student Katayoun Afshar, and UC San Diego colleagues Nelson Barton and Lawrence Goldstein. "A paradigm has shifted. This will change the way people think about chromosomes," says Hawley. "It also has a major impact on how people think about the origin of genetic diseases." Similar findings in frog cells are highlighted along with the fruit fly report in an accompanying scientific review by Margaret Fuller, a researcher at Stanford University. These findings in frogs and fruit flies are believed to be widely applicable because many of the fundamental activities of cells are similar in all animals. Correct division of chromosomal DNA, the genetic material that biologically directs how we are made, is essential to making good eggs and healthy offspring in all animals, including humans. When chromosomes fail to line up correctly during cell division, DNA can be lost, causing genetic diseases such as Down's, Turner's, and Klinefelter's syndromes. As egg cells divide, the chromosomes pair up along the middle of the cell and exchange crossed-over parts, like a bizarre dance where partners line up to pair and exchange hands. Pairing and exchange are critical to the subsequent correct division of the DNA. Evidence has suggested that another, previously unidentified, force assists this process. According to the new findings, the unidentified force is provided in fruit flies by a motor protein called "Nod." When cells lack the Nod motor, chromosomes wander and get lost during division. Motor proteins are just what their name implies, tiny chemical motors that crawl along tracks while carrying cargo. Like James Bond or Batman, who regularly propel themselves into or out of a sticky situation by riding a rope with a hand-held motor, chromosomes can catch a ride to another part of the cell on a microtubule track using motor proteins such as Nod. Hawley and his colleagues discovered that the Nod protein carries a cargo of DNA. "This finding of motors along the chromosomal arms has been found in widely divergent organisms," says Hawley, referring to related findings and a review article published in the same issue of Cell. "This is a general class of proteins that all chromosomes are likely to have." The Hawley lab has studied the Nod motor protein for years and it is the focus of Afshar's research. Her curiosity about this novel protein has paid off with a discovery that will be taught in textbooks and classrooms throughout the world, according to Hawley. This research is funded by the National Institutes of Health and the National Science Foundation. -