Scientists in Iceland have produced a comprehensive portrait of the nation's genetic makeup.
In the process, the team have uncovered several new gene mutations linked to disease as well as revised the estimated age of the most recent male ancestor of all humans.
They were able to extrapolate, or 'impute', the genomes of a further 104,220 individuals - a third of Iceland's population - by cross-referencing partial sequence information with the country's impeccable genealogical records. The results, published across four papers in Nature Genetics, have revealed genetic contributors to Alzheimer's, liver, thyroid and heart disease.
Iceland's near-perfect, centuries-long records on genealogy, coupled with a near lack of immigration and ability to access the national medical records of the volunteers made it a treasure trove of information for the geneticists. In particular, this homogeneity of population - free from background 'noise' - made it much easier to discover rare disease-causing genetic mutations.
For example, by combining hospital records with genome sequencing data, the team found that a mutation in a gene MYL4 strongly correlated with early-onset atrial fibrillation, a heart condition that causes an irregularly fast heart rate.
'It's really the completeness of the information - the sequencing data, the clinical information, the phenotypical data, the drug reaction data - that lets you tie it together,' Dr Lisa Brooks of the US National Human Genome Research Institute told Wired.
Among the group's findings was the increased prevalence of a BRCA2 gene mutation in Iceland, which confers a sharp rise in the risk of developing breast and ovarian cancers. The researchers estimate that about 2,000 men and women in the country carry the mutation.
Since current laws governing research instruct complete anonymity and prohibit the company from alerting the affected individuals, a debate about the ethical implications of the findings has ensued.
'We could, in Iceland, at the push of a button find all women who carry mutations in the BRCA2 gene,' Dr Stefansson told the BBC. 'It would be criminal not to take advantage of it and I am convinced that my fellow countrymen will begin to use it pretty soon.'
He added that he is now in discussions with Icelandic officials about what steps to take next.