We all have hundreds of DNA flaws
Every humans has 400 flaws on an average in their DNA, geneticists say.
According to the UK researchers, most are "silent" mutations and do not affect health although they can cause problems when passed to future generations, while are linked to conditions like cancer or heart disease that appear in later life.
The evidence comes from the 1,000 Genomes project, which is mapping normal human genetic differences, from tiny changes in DNA to major mutations.
In the study, 1,000 seemingly healthy people from Europe, the Americas and East Asia had their entire genetic sequences decoded, to look at what makes people different from each other, and to help in the search for genetic links to diseases.
"All of our genomes contain flaws; some of us will carry deleterious variants but will not be at risk of acquiring the associated disease for one reason or another," the BBC quoted Dr Chris Tyler-Smith, lead researcher from the Wellcome Trust Sanger Institute as saying.
The new research compared the genomes of 179 participants, who were healthy at the time their DNA was sampled, with a database of human mutations developed at Cardiff University.
It revealed that a normal healthy person has on average about 400 potentially damaging DNA variations, and two DNA changes known to be associated with disease.
"Ordinary people carry disease-causing mutations without them having any obvious effect," Tyler-Smith said.
"In a population there will be variants that have consequences for their own health," he added.
The research gives an insight into the "flaws that make us all different, sometimes with different expertise and different abilities, but also different predispositions in diseases," Prof David Cooper of Cardiff University, the other lead researcher of the study, said.
"Not all human genomes have perfect sequences," he said.
"The human genome is packed with pervasive, architectural flaws," Cooper added.
The study has been published in The American Journal of Human Genetics.