You’re Flawed: Geneticists have long known that everyone’s genome contains mutations, but now those flaws have been counted: On average we each have about 400.

Most of these mutations are “silent” — and harmless. But others, on average about two per person, are linked to diseases. Other mutations can make a person more vulnerable to disease and can become problematic when passed onto children.

The new research, published in The American Journal of Human Genetics,

compared the genomes of 179 healthy participants with a database of human mutations. It is part of the 1,000 Genomes Project, which is mapping human genetic differences among the genomes of 1,000 subjects from Europe, the Americas and East Asia.

“Not all human genomes have perfect sequences,” David Cooper of Cardiff University told the BBC. “The human genome is packed with pervasive, architectural flaws.”