Viruses Origins and Evolution
By Amita Vadlamudi
A virus is a tiny parasite that cannot reproduce itself. Once it comes in contact with a vulnerable cell, a virus can dominate and direct the host’s biological systems to produce more viruses.
The evolutionary history of viruses has been of particular interest to virologists and cell biologists. Due to the diversity and extensiveness of this one topic, years have been spent understanding how viruses emerge and develop over time.
Some viruses are observed to have RNA and DNA genomes. Furthermore, a wide range of viruses are known to have singlestrand or double-strand genomes. Despite their disparate characteristics, some common features include their small size and replication abilities.
There is an ongoing debate about the origins of viruses. However, the three primary hypotheses devised are:
1. Progressive or Escape Hypothesis: This means that viruses emerged from genetic elements that could move between cells. The process studies the movement of retrotransposons, a genetic element that makes up 42% of the human genome and can move through an RNA intermediate. 2. Regressive or Reduction Hypothesis: This is opposite to the progressive process and states that viruses are the remains of cellular organisms. Scientists generally agree that certain
bacteria evolved from free-living ancestors. As an extension of this explanation, they infer that viruses may have evolved from a more complicated, but free-living organism.
3. Virus-First Hypothesis: This hypothesis is contrasting to both progressive and regressive explanations which assume that cells existed before viruses. However, the Virus-First hypothesis suggests that viruses may have emerged before cells, possibly being the first replicating entities out there.
Despite years of research that has gone into the study of cells and viruses, there is no factual evidence that justifies any one of these theories. They may have emerged from mobile genetic elements, been descendants of free-living organisms or initiated the existence of cellular life. Regardless of the complexities and confusion, cellular studies still spark great interest in virologists, and future studies may reveal the answers to such questions.
Author: Amita Vadlamudi