A normal healthy person has an average of 400 flaws in their DNA, according to a new study in The American Journal of Human Genetics.

Many are considered “silent” mutations and do not impact a person’s well-being, however, when passed on to offspring, issues may occur. The other flaws, on the other hand, are associated with cancer, heart disease, conditions that occur when a person is older.

The finding came from the 1,000 Genomes project, which is outlining the normal differences in the genetics of humans, from little alterations in DNA to serious mutations.

The project analyzed 1,000 healthy individuals from North America, South America, East Asia, and Europe who had their complete genetic sequences decoded so that the researchers could compare one person’s to another. They were also looking for genetic links to diseases.

For the current study, the genomes of 179 healthy subjects were compared to a database of human mutations developed at Cardiff University.

The results showed that healthy people have an estimated 400 DNA variations that are potentially harmful, and two DNA alterations linked to disease.

Dr. Chris Tyler-Smith, a lead author and from the Wellcome Trust Sanger Institute, Cambridge, said:

“Ordinary people carry disease-causing mutations without them having any obvious effect. In a population there will be variants that have consequences for their own health.

According to Professor David Cooper of Cardiff University, the study expands our knowledge on “flaws that make us all different, sometimes with different expertise and different abilities, but also different predispositions in diseases.”

“Not all human genomes have perfect sequences. The human genome is packed with pervasive, architectural flaws,” he said.

Scientists have been aware that humans have some genetic mutations which seem to result in little damage, or none at all. The majority of these mutations are only harmful if they are passed on to offspring who also receive a duplicate of the identical flawed gene from the other parent.

The team discovered that for every 1 in 10 people analyzed:

  • the mutation is inactive
  • the mutation results in a mild condition
  • the mutation does not have an impact until later life

In the future, the database at Cardiff University, as well as other data on human mutations, will have increasing significance as personalized medicine plays into effect.

The majority of people have their genetic information available to them, while several companies on the internet even provide screening of selected gene alterations.

Since the samples in the 1,000 genomes project were nameless, the subjects will not find out about any gene changes associated with disease.

However, moral concerns are going to become a problem as DNA sequencing grows more extensive, because people will want to know about their genes and the risks associated, while several risks remain unknown.

Dr. Tyler-Smith concluded:

“Should incidental findings be fed back to people who have volunteered their sample to a study? There is no clear answer to this question. 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. For others, there will be health consequences, and early warning could be useful, but might still come as an unwelcome surprise to the participant.”

Written by Sarah Glynn