More than 8,000 Icelanders carry a gene that is completely inactivated by mutations.

Patrick Sulem, Kari Stefansson and their colleagues at deCODE Genetics in Reykjavik sequenced the genomes of more than 2,600 Icelanders and used this to infer the genetics of another set of more than 100,000 people from Iceland. They found that 7.7% of this second set have low-frequency mutations that knock out both copies of at least one gene from a collection of almost 1,200 genes. Genes expressed in the brain and placenta were least likely to have lost their function. The most common type of knocked-out gene was involved in smell.

The next step is to study individuals with different gene knockouts to see what effects, if any, these mutations have on physiology and health.

Nature Genet. http://dx.doi.org/10.1038/ng.3243 (2015)