1 percent of human genes are switched off

LONDON - Scientists studying the human genome have found that each of us is carrying around 20 genes that have been completely inactivated, suggesting that not all switched-off genes are harmful to health.

A team at Britain's Wellcome Trust Sanger Institute is developing a new catalog of so-called "loss-of-function", or LoF, gene variants to help identify new disease-causing mutations and say their work will help scientists better understand the normal function of human genes.

Working as part of larger study called the 1000 Genomes Project, the team developed a series of filters to identify common errors in the human genome, which maps the entire genetic code.