1% not 0.1% — differences in human DNA

“Instead of 99.9% identical, maybe we’re only 99% (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% 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 websites.

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% alike. The new paper suggests estimates of 99.5% to just 99%, Venter said.

The Venter paper joins several others published over the past three to four years that indicate an estimate of around 99%, 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% 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% when the more recently discovered kinds of DNA variation are considered, Venter said.


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