Findings by researchers from University of Michigan and Tufts University.
By Dileep Thekkethil
A new study has ruled out our general perception about DNA as researchers now say that they found 19 new pieces of non-human DNA left behind by viruses that infected ancestors probably hundreds of thousands of years ago, reported Mint.
According to the study conducted by researchers from University of Michigan and Tufts University on about 2,500 people, 50 of their subjects had one stretch of newfound DNA housed with full genetic recipe for an enter virus.
Even though the researchers are not entirely sure about whether they will be able to reproduce the same virus, earlier studies have found that virus DNA could affect the humans who carry it.
The researchers also confirmed that in addition to the new stretch of virus DNA, 17 other pieces of virus DNA were earlier found in human genomes by scientists.
The study claims that researchers collected DNA samples from people of all races, including from people in Africa, which is believed to be the birth place of human beings thousands of years ago.
Researchers say that they used sophisticated techniques for comparing the DNA of each person to the reference DNA, which is otherwise called genome. The findings add to what science already knows about human endogenous retroviruses (HERVs).
HERV is the name for the ancient infectious viruses that comprise a significant part of the human genome, with approximately 98,000 ERV elements and fragments making up 5-8%. The viruses listed in HERV are part of the same type of virus that includes the modern human immunodeficiency virus, which causes AIDS.
According to the study, the virus imprinted DNA kept on repeating and passing down over generations as humans reproduced, ending in the genomes of the current generation of humans.
About 8% of what we think of as our “human” DNA actually came from viruses says the study.
The researchers also added that in some cases, the HERV sequences in the human DNA also serves useful purpose as it helps pregnant women’s body build cell layers around a developing foetus guarding it from toxins in the mother’s blood, they said.
The new HERVs are part of the family called HERV-K. The human endogenous retrovirus type K (HERV-K) family comprises 30-50 members per haploid genome in humans and is highly conserved in Old World monkeys and apes. It is only the second intact provirus found to be hiding in human DNA, researchers said.
“This one looks like it is capable of making infectious virus, which would be very exciting if true, as it would allow us to study a viral epidemic that took place long ago,” said John Coffin from Tufts University.
“This research provides important information necessary for understanding how retroviruses and humans have evolved together in relatively recent times,” Coffin said.
The findings were published in the journal PNAS.