October 29, 2014 | In the early days of genetics, discoveries about the roles of genes often came from finding flies, mice and other animals with rare loss-of-function variants that completely knocked out a particular gene's function, resulting in strange mutant phenotypes. Today, with mass sequencing of humans a practical reality, the hunt is on for loss-of-function variants with more subtle effects circulating naturally in the human population. With every individual in the world carrying an estimated 20 genes with loss-of-function mutations inherited from both parents, some of which appear to be mildly protective against major chronic diseases, very large sequencing studies searching for these variants could eventually lead to new drug and therapeutic targets. Nature News