The complete genome sequence of one person—one of the US biologists working on the project, J Craig Venter—was published for the first time this week. By enabling scientists to compare the contribution of each of the parental chromosomes, it showed that genetic variation among humans was much greater than previously estimated.

The data indicate that variation from human to human is about 0.5% of the genome, not 0.1%, as previously thought.

The new genome, called HuRef (which stands for human reference), is the first time that the full or diploid genome, consisting of the DNA in both sets of chromosomes (one from each parent), has been published for one individual (PLoS Biol 2007;5(10):e244 doi: 10.1371/journal.pbio.0050254). Two previous versions of the human genome, published by the Human Genome Sequencing Consortium and by Celera Genomics, were mosaics of DNA sequences from several donors.

Data on more than 20 …