AMSTERDAM, Netherlands — Dutch scientists say they have completed the first sequencing of an individual woman's DNA.
The researchers at Leiden University Medical Center reported the sequencing of the entire genome of one of their female researchers, clinical geneticist Marjolein Kriek.
"If anyone could properly consider the ramifications of knowing his or her sequence, it is a clinical geneticist,” Professor Gert-Jan B. van Ommen, leader of the research team and director of the Center for Medical Systems Biology, said in a news release issued Monday.
The first sequencing of a composite human genome was announced in 2001. At least four individual male genomes and those of about a dozen animals have so far been sequenced.
Women don't possess the male Y chromosome, but instead have two X chromosomes. Van Ommen said that could lead to genomic differences between the sexes.
"As the X chromosome is present as a single copy in half the population, the males, it has undergone a harsher selection in human evolution. This has made it less variable," he explained. "We considered that sequencing only males, for 'completeness,' slows insight into X-chromosome variability. So it was time, after sequencing four males, to balance the genders a bit."
How much, how long?
The researchers said the cost of the project was 40,000 euros ($63,000). That price tag does not include in-depth genomic analysis, which is expected to take another six months.
"The sequencing itself took about six months," said Johan den Dunnen, project leader at the Leiden Genome Technology Center, "partly since it was run as a 'side operation' filling the empty positions on the machine while running other projects. Would such a job be done in one go, it would take just 10 weeks."
No other scientists have yet verified the Dutch data, but some experts said they were eager to see the sequence.
"The more data that is made public, the more chances we have of making sense of the similarities and differences between them and to understand the patterns of how genes work together," said Stephen Scherer, a genetics expert at the Hospital for Sick Children at the University of Toronto. Scherer was not connected to the Dutch research.
Scherer said that it was important to have comparative genome sequences from women.
In the next few years, he predicted, thousands of genomes would be sequenced. "I think the tipping point when we start to understand how this works will come really fast," Scherer said. "It will absolutely make a difference to how diseases are prevented or treated."
The full complement of an organism's DNA is called its genome. In animals and people, it is made up of nearly 3 billion building blocks. The sequence of those blocks spells out the hereditary information, just as strings of letters spell out sentences. Decoding a genome, which is called sequencing, means identifying the order of the building blocks.
Scientists have made great advances recently in identifying genes for certain diseases such as cancer — and that knowledge is being translated into new types of treatments.
This report includes information from The Associated Press and msnbc.com.
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