Photo: Chris Lund The blood of a thousand Icelanders.

When the first Viking explorers began settling Iceland, none could have imagined that theirdescendants would pioneer thefuture of modern medicine by surveying the human genome. Fast forward 1000 years to today, whenanIcelandic company has revealedits success insequencing the largest-ever set of human genomes from a single population. The new wealth of genetic data has already begunchanging our understanding of human evolutionary history. It also sets the stage for a new era of preventive medicinebased on individual genetic risks fordiseases such as cancer and Alzheimers disease.

Themilestone in genome sequencing comesfromdeCODE Genetics, a biopharmaceutical company inReykjavk, Iceland. Theirwork, published as four papers in the 25 March 2015 issue of the journalNature Genetics,has yielded new insights aboutthecommon human ancestor for the male Y chromosomenarrowed tosomewhere between 174,000 and 321,000 years agobased on their latest calculation of human mutation rates. Another part of their work discovered thatabout 7.7 percent of the modern-day population has rare knockout genesgenes that have beendisabled by mutations. Early research has also revealed a mutation in theABCA7gene,whichdoubles the risk of Alzheimers disease in Iceland and other populations dominated by European ancestry.

These are just a handful of observations that have come out of the ability to look at the sequence of the genome of an entire nation,saidKari Stefansson, founder of deCODE Genetics, during a press briefing onMonday, 23 March.What is more, we are now sitting in Iceland with the possibility of taking advantage of these insights when it comes to the Icelandic healthcare system.

The company sequenced thewhole genomes of 2636 Icelanders and used those genomes as the basis for calculatingthe genetic variances for the entire Icelandic population.Iceland represents a unique laboratory for genetics researchers because much of the modern population traces its lineage to a relatively small number of founders; a fact that makes it easier to trace genealogies and pedigrees.

Myles Axton, chief editor ofNature Genetics, introduced the Monday press briefingbydescribing how the genetic sequencing strategy in Iceland could also work for other countries:

This strategy of sequencing the DNA of about 1 in 100 of the population, a total of 2,636 Icelanders, and then using shared sets of common genetic variance to predict the full spectrum of genetic variance carried by the whole population, is a great model for the future of human genetics. This technique can be applied to any population and is all the more accurate when there are pedigrees available for much of the population.

Genome sequencing has alloweddeCODE Genetics to begin data-mining information about how certain genes function and their relationship to a broad array of diseases. Past findings from such research included additional insights about gene variants associated with Alzheimers disease and schizophrenia.

The growing database on knockout genes may prove particularly helpful when matched against the phenotypes of individualsthe physical traits or characteristics that can be observed. Perhaps unsurprisingly, the researchers found that knockouts are least common among genes expressed in the brain, given that organs importance.

Basically what we hope to get out of phenotyping the carriers of these knockouts is to figure out which biochemical pathways are necessary for which physiological functions, Stefansson explained.Then the question is whetherthere is redundancy in some of these physiological functions;are there alternative biochemical pathways that can compensate for the loss of one?

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Iceland's Giant Genome Project Points to Future of Medicine