X = Y

Scientists have long believed that the genes on the Y chromosome — the genetic carrier of maleness — mutate much faster than their counterparts on its female-oriented counterpart, the X chromosome. (Women normally have two Xs and men an X and a Y.) The conclusion has been that most evolutionary change is driven by genetic alterations in males. Not so, says David Page, an MIT professor and a staff member at the MIT-affiliated Whitehead Institute.

Page calculated the genetic changes over a 1 million to 2 million year span on a large chunk of DNA on the Y chromosome. He did the same with the exactly comparable segment of the X chromosome. Page found that the male DNA had mutated less than twice as rapidly as its X-based counterpart — not five times as fast, as previously thought. He says the finding suggests that the contributions from women to the evolution of our species are about the same as those from men.


An MIT-headed international team has designed a satellite whose aim is to solve a cosmic mystery: the origin of the mega-explosions known as gamma-ray bursts. These cataclysmic events take their name from the fact that they put out prodigious quantities of gamma rays, which are similar to X-rays but pack more punch. With a single explosion releasing as much power as a billion trillion suns, the bursts are “the most energetic events since the Big Bang,” says MIT senior research scientist George Ricker. Team leader Ricker and the rest of the 20-member group hope to render gamma-ray bursts useful as super-powerful “beacons” that can offer a window on the universe’s early days, when large-scale structures were first forming. The satellite they’ve created, the High-Energy Transient Explorer 2, scans the heavens and relays data about any burst identified to ground-based receiving stations. From there, the data goes to MIT, and then on to a NASA center for dissemination on the Internet. The hope is that ground- and space-based observatories will take a close look at the presumed origin of such a burst, thereby helping show what caused it. The satellite is expected to be in business until 2004.


The matter that makes up everything in the visible universe, including the human body, is itself made up of tiny subatomic particles. Two especially key ones are the proton and the neutron. But though MIT physicists Jerome Friedman and the late Henry Kendall shared a Nobel Prize with a Stanford colleague for showing that these particles are made up of still smaller entities called quarks, no one understands in detail how they’re put together. A group of scientists at MIT and elsewhere, in a collaboration with Compaq Computer of Houston, is now mounting an effort to find out. Using a cluster of specially designed high-speed computers, they’re undertaking the complex computations needed to calculate the structure of basic particles from first principles. In the process, they hope to work out whether the so-called theory of strong interactions accurately describes the quark structure of matter. John Negele, professor of physics and a member of the MIT Laboratory for Nuclear Science, leads the team of 22 physicists at 13 institutions involved in the project.


Hormone-like serotonin is a brain chemical with major impacts on how we live our lives. Scientists have found that its effects on the brain are linked to our moods, to how hungry we feel, to the susceptibility of some to migraine headaches, and even to conditions like schizophrenia. Now, MIT researchers have found a new way in which serotonin may act in these and other arenas. The group has discovered a new type of “fast receptor” — a binding element that lets brain chemicals quickly influence the state of selected brain cells — for serotonin. Importantly, when serotonin connects with this receptor, the result is opposite that of the first such receptor identified: instead of activating cells, it becomes capable of shutting them down. Biology professor H. Robert Horvitz, who heads the research group, says the work may someday yield strategies for combating a range of brain disorders.