Leiden scientists sequence first ...( Geneticists of Leiden University Med...)

Geneticists of Leiden University Medical Centre (LUMC) are the first to determine the DNA sequence of a woman. She is also the first European whose DNA sequence has been determined. This has been announced by the researchers this morning, during a special press conference at Bessensap, a yearly meeting of scientists and the press in the Netherlands.

Following in-depth analysis, the sequence will be made public, except incidental privacy-sensitive findings. The results will contribute to insights into human genetic diversity.

The DNA is that of dr Marjolein Kriek, a clinical geneticist at LUMC. If anyone could properly consider the ramifications of knowing his or her sequence, it is a clinical geneticist, says professor Gert-Jan B van Ommen, leader of the LUMC team and director of the Center for Medical Systems Biology (CMSB), a center of the Netherlands Genomics Initiative.

Van Ommen continues: Moreover, while women dont have a Y-chromosome, they have two X-chromosomes. 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. We considered that sequencing only males, for completeness, slows insight into X-chromosome varialibity. So it was time, after sequencing four males, to balance the genders a bit. He smiles: And after Watson we also felt that it was okay to do Kriek.

The DNA sequencing was done with the Illumina 1G equipment. This has been installed in January 2007 in the Leiden Genome Technology Center, the genomics facility of LUMC and CMSB. In total, approx. 22 billion base pairs (the letters of the DNA language) were read. That is almost eight times the size of the human genome.

Dr. Johan den Dunnen, project leader at the Leiden Genome Technology Center: 'This high coverage is needed to prevent mistakes,
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