People Not 99.9 Percent Identical After All

In 2000, at a White House press conference on genetic discrimination, the head of the National Human Genome Research Institute, Francis Collins, declared, "Mr. President, I know that you know that you and I, like any other two Americans, regardless of ethnic group, are 99.9 percent genetically identical."

The impulse behind this declaration was not so much scientific as it was designed to forestall racist interpretations of the findings of genomic science.

The Philadelphia Inquirer is now reporting on recent research that shows that it isn't quite that simple. That people's individual genomes are, well, individual. This will prove to have all sorts of consequences for interpreting human diferences, especially in the area of treating diseases. According to the Inquirer:

It was a nice idea that we're all genetically 99.9 percent identical, but new research says it's not so simple.

The old thinking held that coiled in our cells, we all carry the same instruction book with just a few alternative spellings. But upon closer scrutiny, it appears our DNA is full of long strings of genetic code that are copied sometimes hundreds of times, the number of copies varying wildly from person to person.

And each of us is apparently missing quite a few large chunks of DNA. Other large segments of genetic code are misplaced on their chromosomes or pasted in backward. Not that there's any one designated normal arrangement—we're all just different.

As this all was becoming clear over the last several years, scientists expressed some surprise that the human genetic code is such a disorganized mess.

"This changes how we think about evolution and, in some respects, disease," says Evan Eichler, a researcher at the University of Washington, Seattle. "That's the part that's exciting."

Whole thing here.