'Alien' DNA Strands Discovered in Human Genome

Science has already successfully mapped the human genome and identified the functions of specific genes in hereditary characteristics, such as skin color. But few people know that some of the DNA strands in the human genome are not even human in origin, making them quite "alien."

A recent research paper published in the Proceedings of the National Academy of Sciences has revealed that the human genome contains at least nineteen pieces of ancient viral DNA. More so, complete genetic strands of the viruses were found in two percent of the people who were tested.

The ancient genetic fragments from viruses found in our genome are known as human endogenous retroviruses, or HERVs. The study examined the genome of 2,500 people across the globe and found genetic markers for HERVs.

Approximately eight percent of the DNA in the human body is from viral genetic fragments. These are the DNA strands that became integrated with the human genome and passed on to several generations.

The ancient viral fragments can be traced back to ancient chordate ancestors of humans. These viral DNA strands influenced evolution over millions of years.

The most common types of viruses are the retroviruses that have RNA instead of DNA. But their genetic codes can be translated into DNA equivalents by just replacing one nucleotide, which is uracil.

Viruses need host organisms in order for them to replicate. In the process, some fragments of the viral genetic codes were embedded in the strands of DNA of their hosts. The cells of infected organisms inadvertently reproduce the genetic codes of the viruses.

Our ancient ancestors have been infected by a wide range of retroviruses for several hundreds of thousands of years. Some of our ancestors passed on the modified genome to their descendants, including us now alive in the present.