Viruses can evolve fast and sometimes adapt quickly to a new host species. For example, an influenza virus that normally infects birds can become adapted to humans. The tobacco etch virus normally infects tobacco plants. Professor Santiago Elena from Valencia wants to find out what it takes to make the tobacco virus capable of infecting another plant: Arabidopsis, a small flowering plant. The movie shows how the scientist does the evolutionary experiment.
At the beginning an Arabidopsis plant is infected with the Tobacco virus. At this point, almost nothing happens, because most of the virus dies out. But by random chance, a few virus individuals could carry mutations, allowing them to survive. The remaining virus is extracted and used to infect another Arabidopsis. After 30 times, continuously infecting, then extracting the virus will the new virus be different from the original one? Has evolution taken place? The final step of the experiment will reveal that the virus is indeed adapted to the new host plant! After the experiment, Elena looks at the genetic code of the adapted virus and finds that there are just three differences between the genetic code of the normal (tobacco loving) virus and the virus that is now adapted to Arabidopsis.
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