Sex in humans is determined by the fact men carry one X chromosome and one Y chromosome in each cell, while women carry two Xs.

David Page of the Whitehead Institute has recently shown that Y chromosomes can repair its own genes in an experiment that denied the Y chromosome the benefits of recombining with the X.  The result was that the Y recombined with itself.  Dr. Page's team also found 78 active genes on the Y, contradicting earlier impressions of the chromosome as being a genetic wasteland apart from its male-determining gene.

In related news, MIT and Harvard announced today the formation of The Broad Institute whose purpose will be to fulfill the promise of the Human Genome Project for medicine.  As Charles M. Vest, president of MIT noted, “This venture will be an important nexus of Boston and Cambridge’s contributions in the future. We are deeply grateful to Eli and Edye Broad for their visionary commitment ($100m immediately) and for their extraordinary leadership as philanthropists."