Pairing up: how chromosomes find each other

Meiosis—a special type of cell division—cuts in half the number of chromosomes carried by an individual’s regular body cells. It allocates precisely one copy of each chromosome to each egg or sperm cell, thus ensuring that the proper number of chromosomes is passed from  parent  to offspring.  And because chromosomes come in pairs— twenty-three sets in humans—the chromosomes must be properly matched before they can be divvied up.

In a recent study, Stowers researchers shed light on how fruit fly chromosomes line up to prepare for meiosis. First, they gather their centromeres, the anchor points that control the separation of chromosomes when cells divide,  in one corner of  the nucleus. Once chromosomes have paired up — chromosome 1 handed  down  from the mother with chromosome 1 handed down from the father and so forth—they initiate the formation of the synaptonemal complex, a “protein-zipper” that runs the entire length of each pair of chromosomes.

“Understanding this and other mechanisms involved in meiosis is important because of the crucial role meiosis plays in normal reproduction—and the dire consequences of meiosis gone awry,” says Stowers Investigator R. Scott Hawley, PhD.  “Failure of the meiotic division is probably the most common cause of spontaneous abortion and causes a number of birth defects such as Down syndrome.”

The study appeared in the November 8, 2011, issue of Current Biology.