By Marlowe Hood
Paris: The first individual genome ever sequenced -- a complete DNA blueprint of celebrity scientist Craig Venter -- has revealed genetic variation among humans far richer than previously imagined.
Published on 4 September in the online open-access journal PLoS Biology, the 2.8 billion contiguous bits of genetic code will also hasten advances in preventative medicine, said Venter, who is both an author and the object of the study.
Within five years, faster and cheaper sequencing techniques could produce complete genomes for 10,000 people, laying the foundation for “an era of individualized genomics,” he predicted.
“Once we have those, we will basically be able to sort out every fundamental question about nature versus nurture, what’s genetic and what’s environment,” he said by phone.
The findings overturn what had in a few short years become genetic gospel: that all human beings are, genetically speaking, 99.9 identical.
Venter himself trumpeted this idea in 2000 when his biotech firm Celera, which he left in 2003, and a team of US-government scientists simultaneously unveiled -- after a bruising race to the finish line -- the fist complete human genome.
Both of these earlier efforts were flawed and greatly underestimated genetic diversity, he and his colleagues now say, because the whole had been assembled from a hodgepodge of DNA taken from several individuals.
The variations revealed in the new genome, dubbed, “HuRef”, go far beyond previously identified single nucleotide polymorphisms (SNPs), once thought to be the key to differences in human traits and disease susceptibility.
SNPs are DNA sequence variations that occur when a single nucleotide -- the basic building blocks, composed in pairs, of DNA -- in the genome sequence is altered.
Also important, however, are previously overlooked variations in stretches of genetic code that were once dismissed as useless “junk DNA”.
“This dispels the notion we had in 2000 and 2001 that we all have exactly the same genes in the human population,” said Venter. “It would have been very disturbing if the range of characteristics that we see all came down to a few simple SNP variations.”
The new data shows that in an individual genome upwards of 44% of genes are variable in sequence.
“This is a number that geneticists and biologists have been wondering about for 50 to 100 years,” commented co-author Stephen Scherer, a geneticist at The Hospital for Sick Children in Toronto.
“HuRef” was built on the foundation of Venter’s earlier project, which was already 60% composed of his own DNA. But it still took an additional $10 million and three years to complete.
To spur more efficient technologies, Venter has contributed $500,000 to the $10 million Archon X Prize for scientists who come up with genome sequencing techniques that are rapid, accurate and inexpensive.
Some ethicists have expressed concerns about the possible abuse of personal health information that may be easily accessible once coding individual genomes becomes routine.
The study itself raises the issue, if only indirectly: a table listing some of the traits commonly associated with certain genes expressions found in Venter’s genome reveals more than some people might care to.
A genetic propensity toward Alzheimer’s and cardiovascular disease, for example, prompted Venter to take statins, a compound thought to help forestall both conditions.
But that same information -- or the fact that one tends toward tobacco addiction or alcoholism, other traits identified in the study -- could be seen in another light by potential insurers or employers, critics point out.
For Venter, the possible advantages far outweigh such concerns.
“We have all been taught that we should fear this information. We hope to teach people they should welcome it as a breath of fresh air that gives them opportunities in their lives.”
He did, however, allow for the possibility that anybody’s genome information “is relatively easy to get.”
Other researchers who worked on the three-year project at Venter’s eponymous institute came from the University of Barcelona and the University of California at San Diego.