MYSTERIES OF THE X CHROMOSOME
By Robert Lee Hotz
Los Angeles Times
Scientists have found an unexpectedly large genetic variation on the X chromosome among women, according to a study published today in the journal Nature.
The findings were published in conjunction with the first comprehensive decoding of the chromosome, which appeared in the same journal.
Females can differ from each other almost as much as they do from males in the behavior of many genes at the heart of sexual identity, researchers said.
``Literally every one of the females we looked at had a different genetic story,'' said Duke University genetics expert Huntington Willard, who co-wrote the study. ``It is not just a little bit of variation.''
The analysis also found that the obsessively debated differences between men and women are, at least on the genetic level, even greater than previously thought.
As many as 300 of the genes on the X chromosome may be activated differently among women than among men, said molecular biologist Laura Carrel at Pennsylvania State University College of Medicine, the other author of the paper.
All told, men and women may differ by as much as 2 percent of their entire genetic inheritance. That degree of difference is greater than the hereditary gap between humankind and its closest relative -- the chimpanzee.
``In essence,'' Willard said, ``there is not one human genome, but two -- male and female.'
-Arlos
