Had one of his parents been slightly less fortunate in their choice of a mate, James Watson might not have helped discover the structure of DNA in 1953. Instead, he would have been born deaf and then lost his sight as he became a teenager. Equally, as he is, had he been less fortunate in the genetic lottery when he chose his wife, either of their sons might have had the same fate.
This is because Watson’s complete DNA — his genome — contains a single gene for Usher’s syndrome, an inherited disorder that affects hearing and sight. Watson’s must have come from one of his parents. Usher’s is a “recessive” disease — you need two copies of the gene to be affected. About five people per 100,000 carry the gene, so Watson’s chances of being disabled weren’t large. But they were real.
We know this because the analysis of his genome was made public this month in a groundbreaking paper in the science journal Nature that also revealed that he carries genes that may increase his risk of cancer, including one linked to breast cancer. While the sequencing of genomes for research has become almost routine — so far the genomes of dozens of species have been sequenced — Watson’s was notable for how quickly and cheaply it was done.
The first full human genome sequencing, completed in 2003, took 13 years and cost US$437 million. Watson’s sequencing, carried out by a company called 454 Life Sciences, took only two months and cost about US$1 million. Other companies, such as Illumina and Applied Biosystems, are relentlessly pushing the cost down.
Reading the 3 billion “base pairs” in human DNA — akin to letters, encoding a total of between 20,000 and 30,000 genes that are the “words” of genetics — is getting faster as companies find quicker ways to “read” entire stretches of DNA at a time, like reading a sentence in chunks rather than letter by letter. The 454s can read up to 450 bases at a time; Pacific BioSciences, one of many rivals, more than 1,000.
The cost of sequencing an individual genome is thus falling exponentially — just as the cost of hard disk space or transistors on a chip did when computing took off. Plotting the numbers on a graph suggests that by 2012 it will take a few hours and cost less than US$100. A few years after that it will cost perhaps US$10.
That’s when you should expect an explosion in personal sequencing. Jason Bobe, the director of community for the Personal Genome Project, based at Harvard Medical School, writes the Personal Genome blog (thepersonalgenome.com) and reckons that by 2015, 50 million people will have had their own DNA sequenced.
“My rationale is simply to assume that the trend line for the personal sequencing market might look a lot like the one experienced in the personal computer market” — which grew from a few thousand units sold in 1975 to 50 million in 1995, he said.
“If the personal genome sequencing market follows suit, we might say that 2007 for personal genome sequences was like 1979 for PCs and we’ve just turned the corner into 1980 where units sold remains below 1 million, but growth is noticeable,” he said.
Who benefits?
Cheap, fast genome sequencing could upend how we think of disease and identity. If it’s fast and cheap enough, would benefits claimants be asked to provide a DNA swab from their cheek? Would the same swab be your passport? Might police at a crime scene simply scan for DNA?
The first, most obvious, use is fetal testing. Would a future James Watson and would-be spouse compare genomes? If both had single genes for Usher’s syndrome, would they have children anyway, given the one-in-four chance that their child might have the full-blown syndrome? Would abortions be allowed on the basis that a child would have a disabling — but by no means life-threatening — genetic disease? The impending arrival of everyone’s genome only makes this more urgent.
Watson himself, on seeing the presence of his breast cancer gene, said he would have acted on the knowledge had he had daughters.
“I would tell them to immediately check if they had [that mutation],” he said.
But he also chose to withhold parts of the sequence relating to the APOE gene — associated with a higher risk of Alzheimer’s disease — because he doesn’t want to know if he has a genetic disposition to it.
His nuanced approach will be food for thought for the House of Lords select committee on science, which this week opens an inquiry into “genomic medicine.”
Mark Jobling, professor of genetics at the University of Leicester, notes that: “The problem is that many common genetic diseases are complex. It isn’t a single base change. More complex diseases like schizophrenia and Alzheimer’s won’t be predictable.”
The idea of DNA profiling to collect benefits isn’t new. It was suggested by the Labour Member of Parliament Frank Field, then in opposition, as long ago as July 1996, “to safeguard the National Insurance system” — though he insisted that this was not “the introduction of an ID card.”
“A DNA test should be taken at birth along with all the other tests which are now merely a routine,” Field said.
The suggestions caused outrage at the time; but routinely sequencing a baby’s genome at birth will be possible in a decade.
Precisely that suggestion — of routine genomic sequencing of newborns — was suggested in a 2003 policy paper, points out Helen Wallace, director of Genewatch UK.
“It was criticized on cost grounds,” she said, “but more particularly because most of that information [about an individual’s genome] was likely to be misleading. OK, you can tell where someone has recessive genes that might lead to a known genetic illness, but the claims being made now by some of the companies offering sequencing are leading to concern and fear of disease.”
Wallace suggests that they are distractions.
“You share your environment and lifestyle with your family and for most of us this will be more important than our genes,” she said. “Gene tests won’t help to tackle major health problems such as bad diets, poverty, smoking and pollution.”
Genewatch generally opposes universal sequencing, on surveillance grounds.
What about crime scene tests?
“The only reason for doing a full genome sequence would be for phenotype prediction, if you found DNA and didn’t have a match. There have been some genetic variants already discovered that affect height; you might know eyes, hair ... you could produce an identikit predictive picture of your suspect. But in terms of individual ID, [DNA fingerprinting is] already perfectly adequate as it is,” Jobling said.
There’s also the question of how far the price of testing will fall.
“We’ve got a new sequencer here at the university and it cost £250,000 [US$496,000], with an annual maintenance contract of £25,000. And that’s before we’ve switched it on,” Jobling said.
“How far down the cost will go will be determined by the final size of the market and its applications,” he said.
But if the whole population is sequenced from birth and your DNA becomes your passport and benefit ID, that will expand the market.
James Watson may be among the first. But many are sure to follow.
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