A new study that used genetic information from the UK Biobank and personal genetics company 23andMe has reported that a curious genetic condition, uniparental disomy, might be more common than previously thought. Most people with this condition are likely unaware of it and researchers say that while in some cases it can lead to serious health conditions, others might live a perfectly healthy life unaware of it.

DNA, the blueprint of what makes us us, is stored in the nucleus of each cell in our body. It's packaged in structures known as chromosomes and most of us have 46, divided into 23 pairs. Usually, we get 23 from our mothers and 23 from our fathers. But not always.

Uniparental disomy or UDP is one of the conditions where this doesn’t happen. In UDP, one or more chromosome pairs come from just one of the parents instead of a copy from each. This condition was only discovered in 1987, and it was believed to be quite rare. Over the last decade, researchers have been reconsidering if this is actually the case, and suggested that the low incidence rate was actually down to a lack of study.

Now new research published in The American Journal of Human Genetics shows that they were likely right. Previous research suggested that it occurs between one in 3,500 and one in 5,000 people. This new research places the rate of UPD at about one in 2,000. 

“So that’s about twice as common as was previously thought,” lead author Priyanka Nakka, a postdoctoral research fellow at Boston Children’s Hospital and former 23andMe intern, told Gizmodo UK.

The team looked at markers of UPD across 4.4 million consenting research participants from the personal genetics company 23andMe, as well as 431,094 UK Biobank participants. They found 675 people across both groups that have UPD. To establish the incidence rate they looked specifically at parents and their offspring within the database. They found 105 cases among the 214,915 that matched the criteria.

The study provides interesting insights into this genetic condition, and raises the possibility that it may occur more often than we thought, but there are limitations to the study. For example, 23andMe is a private company, so the sample subjects are not representative of the general population. That said, employing such a large database showed up no particular correlation between UPD and deleterious health traits, between which it had been thought there was a link.

[H/T: Gizmodo UK]