Female Supremacy Articles - Page 18

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02:00 AM Mar. 17, 2005 PT

With the publication this week of the gene sequence of the X chromosome, we will start to find genetic reasons for why the sexes are different, beyond XX and XY.

One clue leaps straight out of the mass of sequence data detailing the 1,098 genes found on the X: Of 40 women whose X chromosomes were looked at, all of them showed extensive variation in gene activity.

Huntington Willard, director of the Institute for Genome Sciences & Policy at Duke University in North Carolina, said that this meant that effectively there are two different human genomes, one male and one female.

"We looked at the X chromosomes of 40 women and every one of them had a unique pattern of gene _expression," Willard said. "All of that variation is completely unique to women. The X chromosomes of males are all the same in this regard."

Women (and all female mammals) have two copies of the X chromosome, but the extra copy isn't needed, and is switched off in a process called X inactivation. Or that's what scientists thought.

"Our study shows that the inactive X in women is not as silent as we thought," said co-author Laura Carrel, a molecular biologist at Penn State College of Medicine, in Hershey, Pennsylvania. "The effects of these genes from the inactive X chromosome could explain some of the differences between men and women that aren't attributable to sex hormones."