A large portion of human DNA is believed by scientists to have originated from viruses. This idea is derived from the ability of certain viruses to assimilate parts of its own DNA into the DNA of human cells. An example of this is demonstrated in the Herpes Simplex Virus, also called HSV-1 (oral herpes) or HSV-2 (genital herpes). The Herpes Simplex Virus often causes symptoms such as blister outbreaks erupting out of the affected areas. Lying in the center of the virus cell is the DNA, which is surrounded by an icosahedral capsid, a protein shell which encloses the DNA. This capsid is surrounded by approximately 15 different proteins collectively known as tegument, and all of this is bound by a membrane envelope, which is covered with many spike proteins on the surface of the membrane. These spike proteins are used to connect with the receptor proteins located on the surface of the host's cells, allowing the virus membrane to fuse with the host membrane, dumping the capsid and tegument into the host cell. The capsid then travels down a microtubule scaffold towards the host cell’s nucleus, while also spreading tegument to destroy any mRNA within the host cell, eliminating competition for ribosomes which are used for protein construction. Once the virus reaches the nucleus, the virus DNA is absorbed into the nucleus through a nuclear pore on the surface of the nuclear membrane. The DNA then forms a circular shape. Another tegument known as VP16 then transcripts the virus DNA into mRNA molecules, which then use the freed ribosomes to translate proteins. These proteins then travel back into the nucleus to translate the virus DNA into a different set of mRNA, which is then translated into another unique set of proteins by the ribosomes. These new proteins are then used to replicate the virus DNA, creating another exact copy of the original virus DNA. This new set of DNA then creates more mRNA, which creates new proteins forming a new capsid for the duplicate DNA, as well as covering the endoplasmic reticulum with spike proteins so that when the duplicate DNA leaves through the endoplasmic reticulum, it receives a membrane envelope covered in spike proteins just like the original HSV cell. This new cell is then sent to the golgi apparatus, where it is sent out of the host cell and goes on to infect other cells. This ability of the HSV virus to incorporate its own DNA into human cells leads many scientists to believe that non-coding sections of DNA, also known as junk DNA, are actually ancient artifacts left over from previous evolutionary battles with primitive viruses.