In the July 16 issue of Nature, genetic researchers announced that they had finished sequencing the genomes of two species of parasitic flatworms that cause the disease known as snail fever. The flatworm is just the latest in an expanding list of sequenced genomes that now includes the human, the fruit fly, the mouse, the cat, the duck-billed platypus, various bacteria, and hundreds of other species. How do scientists decide which genome to sequence next? They follow the money. The National Institutes of Health, which helps fund at least half of the nation's genome-sequencing research, regularly receives project proposals from scientists. In a white paper, researchers explain why they want a particular organism sequenced—why it's useful, what they hope to learn, etc. (See a group of scientists make the case for the rhesus macaque.) An NIH advisory committee then decides which proposals to prioritize by looking at several criteria: the odds that the newly mapped genome will improve human health and biological understanding, cost of sequencing, suitability of the organism for experimentation, and demand in the scientific community for the new sequence data. NIH then allocates funds accordingly. (Check out the list of completed, pending, and future sequencing projects.)
Scientists often target organisms that are already used in the laboratory, since their genomes are likely to be the most useful. Accordingly, the mouse, the fruit fly, the zebra fish, and the roundworm were among the first sequenced genomes. (NIH is still going through all the different types of fruit fly.) Researchers may also choose a particular organism in order to compare its genome with one they already have. Such comparisons help reveal which DNA sequences correlate with which physical characteristics, like eye color or having a head. Other times, scientists will compare genomes within a single species. For example, the researchers behind the 1,000 Genomes Project are comparing 1,000 human genomes and examining the variations among them. The Cancer Sequencing Project, meanwhile, compares human genomes to find the DNA coding associated with particular tumor types.
If you have enough money, you can always fund your own sequencing. But the vast majority of funding comes from government agencies. The U.S. Department of Agriculture, for example, put up funds to sequence the horse genome. Australian researchers with help from the NIH sequenced the kangaroo genome. Chinese scientists at the Beijing Genomics Institute, meanwhile, sequenced the giant-panda genome.
How much does sequencing cost? The original Human Genome Project cost $300 million and took more than a decade. But that project established a template that made every subsequent undertaking quicker. These days, you can get a complete individual human genome sequenced for about $50,000. (That doesn't include the fixed costs of the sequencing machine, lab space, etc.) But that cost is plummeting. One independent company will sequence part of your genome—usually the parts related to particular genetic diseases—for $5,000. And some genetic scientists predict that sequencing an entire genome will soon cost $1,000 and take 20 minutes.
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Explainer thanks Adam Felsenfeld and Larry Thompson of the National Human Genome Research Institute.