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Our DNA Is Not 100% Human – Ancient Viruses Infiltrated Us Throughout Centuries

Viruses from the distant past have managed to keep copies of their genetic material right in our own DNA, says a study published in the Proceedings of the National Academy of Sciences.

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Your DNA is not as human as you think — not 100% human anyway. A new study conducted by scientists from Tufts University and the University of Michigan Medical School suggests that our DNA has been infiltrated by viruses throughout the centuries.

Our genes are hiding so much more from us than we can even ever fathom. But, humans will always persevere in trying to grasp in their knowledge what evades them. This is how 19 new bits of non-human DNA have been found right there in between our own genes, after the entire genomes of people from different parts of the world were analysed for the presence of these non-human DNA.

This non-human DNA is thought to be the remnants of viruses that infected our ancestors centuries ago. This type of virus that leaves behind a DNA copy of their own RNA into the human genome is commonly known as human endogenous retrovirus (HERV). The HIV is of this very type of organism. The newly-identified HERVs are from the HERV-K family. If this does not scare you yet, wait to hear about the additional findings.

Among these viral DNA pieces, there is one stretch thereof that constitutes a full genome for an entire virus. This was detected in 50 of the 2,500 participants of the study. It was found on the X chromosome, and has been named Xq21. This is not the first time such a thing has been discovered: another intact whole viral genome has been spotted in human DNA before. It is not yet known as to whether this piece of DNA can replicate. However, previous studies suggest that it can affect the humans in whose bodies they are. The newly-found one might be used to make infectious viruses, point out the researchers. This implies the possibility of studying a viral epidemic that happened centuries ago.

The paper also documented 17 other viral DNA pieces in human genomes that have been identified by other teams of researchers in the past.

These results mean that the DNA that was generated from the virus has been copied and inherited throughout generations of human beings. The researchers suggest that around 8% of what is considered to be human DNA might have actually come from viruses; specially that some HERV DNA sequences might have been taken in by the human body to fulfill a purpose: for instance, one such sequence can be used by the pregnant female body to construct a cell layer surrounding the foetus that shields the latter from toxins present in the blood of the mother.

The study constitutes invaluable information that is expected to shed light on the evolution of retroviruses and humans.

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