This year may be remembered as the year of the personal genome. Last month, two companies announced plans to decode the genomes of individual human beings. A company in Branford, CT, 454 Life Sciences, is sequencing the genome of James Watson, the codiscoverer of the structure of DNA and an eminent figure in the genomics field (see "Sequencing in a Flash"). And Illumina, a DNA analysis company headquartered in San Diego, CA, is sequencing the genome of one of the Yoruba people participating in the international HapMap project, the first effort to probe the structure of diversity in the human genome on a large scale (see "Genes, Medicine, and the New Race Debate," June 2003).

Whereas the DNA sequence produced by the Human Genome Project in 2003 was a mosaic drawn from a number of different human genomes, the efforts by 454 Life Sciences and Illumina, which could be completed in the next few months, will be the first sequences of individual genomes. As such, they herald the era of "personalized genomics." An individual genome sequence shows the particular combination of genetic variants in an individual's DNA, allowing scientists to explore the relationship between a person's genotype and his or her biological traits. This has been done at the level of single genes for decades, but never before on the genome-wide scale.