THE VIRUSES ORIGIN

The position of the virus as a boundary between the living and inert posed to the scientists the problem of its origin. The origin of the modern virus is not entirely clear, perhaps a single mechanism can not answer this question. Since not fossilized, molecular techniques are the most common methods used to hypothesize its origin. Two main hypotheses exist today: The virus would be the first beings in the history of the evolution of the inert to the living, who managed to meet effectively the functions of replication, transcription and translation. Would, therefore, agencies less advanced . The fact that viruses can only do these three vital functions inside living cells, leads to believe the virus could not exist before the emergence of the first cells, no matter how simple they were.
Viruses with only a few genes could be parts of nucleic acid from the genome of an organism. Their genetic material could have been derived from genetic elements transferable, such as plasmids or transposons, which can go in and out of genomes. [47] New virus could emerge at any time, and therefore do not always have the virus ancestors. Viruses with larger genomes, such as poxvirus, may have once been small cells that parasitized cells bigger. Over time, they could not lose the genes required for its parasitic lifestyle in a simplification process known as retrograde evolution. Rickettsia and Chlamydia bacteria are living cells that, like viruses, can be played only within a host cell. The parasitic lifestyle of these agencies has resulted in a loss of genes that in the past would have allowed them to survive outside the host cell. These examples lend credence to the hypothesis of simplification.
The discovery of other forms acelulares has brought new light to the origin of the virus, but has not served to resolve the dilemma posed. The other forms acelulares are:

The proviruses.

Plasmids.

Viroids.
Some scientists (like Temin, in 1969) have postulated that the virus would be the result of the evolution of these forms acelulares: DNA viruses come from proviruses and plasmids, and RNA in viroids. CAPS of the virus would be an evolutionary achievement for which the genetic material would be protected as they move from one cell another, and ensure the success of the infection. On the other hand, forms acelulares could have been born within the cell half, when certain genes to achieve autonomy for the operation of cellular genome, in this way, the origin of the virus would not necessarily linked to episodes that come with emergence of life on earth. But it could also speak of a reverse process: a loss of the Fund to reduce the autonomous units of replication-transcription-translation to the condition proviruses, or plasmids viroids. In conclusion, the discovery of acelulares simpler forms that viruses helps us to better understand their nature and biological significance, but it keeps us on the question of whether we are compared to the first organisms emerged from inert matter, or to form resulting degressive the expertise to parasitism.