For the first time, scientists have decoded and published a nearly complete readout of both sets of chromosomes in an individual. The diploid genome, of biologist J. Craig Venter, reveals much more human genetic variation than scientists had expected.
In 2001, two competing projects, one run by the federal government and the other by a private company, announced the sequencing of the human genome. However, those sequences, or readouts of DNA's letter order, were in essence only half finished.
Individuals inherit two copies of each of the 23 human chromosomes—one copy from each parent. To speed the task of sequencing the human genome, both teams decided to decode only one of each pair. The resulting genomes were haploid, meaning that they represented only half the chromosomes.
"It turns out with the haploid genomes, we missed most of human [genetic] variation," says Venter, who led the project to decode his own genome at the J. Craig Venter Institute in Rockv