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2007-09-04 07:16:03
By MALCOLM RITTER, AP Science WriterMon Sep 3, 8:00 PM ET
People are less alike than scientists had thought when it comes to the billions
of building blocks that make up each individual's DNA, according to a new
analysis.
"Instead of 99.9 percent identical, maybe we're only 99 percent (alike)," said
J. Craig Venter, an author of the study and the person whose DNA was analyzed
for it.
Several previous studies have argued for lowering the 99.9 percent estimate.
Venter says this new analysis "proves the point."
The new work, in the latest issue of PLoS Biology, marks the first time a
scientific journal has presented the entire DNA makeup, or human genome, of an
individual. However, James D. Watson co-discoverer of DNA's molecular
structure received his own personal DNA map from scientists a few months ago.
And the genomes for both him and Venter are already posted on scientific Web
sites.
Venter is president of the J. Craig Venter Institute in Rockville, Md., which
does genetics research. He and scientists at his institute and elsewhere
collaborated on the work that produced his genetic map.
The order of building blocks along a strand of DNA encodes genetic information,
somewhat like the way a sequence of letters creates a sentence. Particular
sequences form genes. Landmark studies published in 2001 indicated that the DNA
of any two people is about 99.9 percent alike. The new paper suggests estimates
of 99.5 percent to just 99 percent, Venter said.
The Venter paper joins several others published over the past three to four
years that indicate an estimate of around 99 percent, said Richard Gibbs, a DNA
expert at the Baylor College of Medicine in Houston who didn't participate in
Venter's study.
The studies produce the lower figure because they uncovered chunks of DNA that
differ among people, whereas previous studies focused on differences in
individual building blocks.
The 99 percent figure is close to what scientists have often estimated for the
similarity between humans and chimps. But the human-chimp similarity drops to
more like 95 percent when the more recently discovered kinds of DNA variation
are considered, Venter said.
Gibbs called the Venter paper significant, along with a similar but
not-yet-published analysis of Watson's DNA that he has worked on. That's
because the analyses show more differences than expected from the standard
human DNA sequence published by the federal government, he said. (The federal
sequence was based on a mix of DNA from different people.)
That finding in turn is shedding light on how DNA varies among people, with
implications for understanding the genetic underpinnings of disease, Gibbs
said.
Although the new paper analyzes just Venter's genetic material, it can make
estimates about how individuals differ in their DNA. Everybody inherits two
sets of DNA, one from each parent. Venter's paper compared the DNA he inherited
from his mother with the DNA from his father.
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On the Net:
PLoS Biology: http://biology.plosjournals.org
Basics of DNA: http://www.dnaftb.org