Eli5-If a virus isn’t technically alive, I would assume it doesn’t have instinct. Where does it get its instructions/drive to know to infect host cells and multiply?
In: 7067
Viruses are just natures flash drives, leave one lying around, a living thing might plug it in. Maybe it’s a flu, maybe a it’s computer program to destroy an uranium enrichment facility
An acid doesn’t have instinct, yet it knows to dissolve metal. Viruses sit on the line between what is simply a chemical reaction, and what is life.
They make us question what it means to be alive. Are we just chemical reactions?
A virus is a simple biological *machine*. It doesn’t “want” anything and doesn’t “do” anything per se, it just happens to be a booby trap that fools actual working cells in your body into creating more copies by switching out the blueprints your cells should create.
Love this question. And I absolutely hate when people allude to, or even specifically indicate that viruses do anything on purpose. It’s math. That’s it. It’s odds. Physics. Chemistry. They do not choose to mutate a certain way or evolve a certain way because they don’t know anything at all.
It doesn’t know anything?
It is proteins. And DNA.
It’s DNA, makes more proteins. Those proteins each get a copy of it’s DNA, then they get released.
It’s all about the DNA. The viral DNA particle’s sequence is naturally good at forming a viral shell around it, which gets it injected into a cell where it makes copies of itself and its shell. Because it’s good at getting replicated in its environment, it persists while less efficient DNA sequences get gradually outcompeted into extinction. There is no will, just chemistry and statistics pushing ever more efficient viruses.
Think of a virus like a chain letter; all it has is packaging (envelope) and a set of instructions.
If a chain letter says “Send this to 10 people, or you will die in 7 days!” Then it can convince some people to go along with copying it and mailing out more letters. The more successful a chain letter is, the more of that chain letter gets produced. The letter itself doesn’t have any intentions, but if it doesn’t get people that receive it to make more letters, then new chain letters won’t be produced and the chain will end.
A good chain letter needs to be packaged in an envelope that won’t be tossed out before being opened (needs to blend in with other mail), and it needs to have an effective call to action to get people to make copies (threats of bad luck or being cursed). Over time, small changes in the text of the letter may occur. Instead of the letter saying the receiver “will be cursed to go deaf”, the letter might be written as “cursed to deaf” and then copied again to “cursed to death”. This change might be totally a result of chance, but new chain letters will now include a different, more severe threat of consequences, and so might be more successful at getting recipients to make new copies of it.
A virus is more complicated, but basically works the same way; it needs to be let into the cell and to get the cell to make copies of the virus. If it doesn’t do so successfully, then the virus will eventually die out. The better a virus is at spreading, the more of it there will be.
Most of the “instructions” come from shape. There are proteins on the outside that attach to proteins that their host have. There are proteins inside that automatically eject the genetic payload when the attachment proteins click into place. The genetic package has then bits that are the right shape to click themselves into the cell structures that will replicate them and build new copies of the virus.
Picture a computer in a small room. You throw a million USB sticks at it and one will land in the reader.
Over millions of instances and millions of years, some code might get swapped. Eventually, the code contained within the USB will start instructing the computer to make more USBs with the same code.
There is no instinct, but survival traits are bred into the code, as the ones that don’t have such traits go extinct.
The scale at which viruses have operated on are unfathomable. Remember, viruses have been around for far longer than humans.
What determines technically alive is a set of man made and arguably arbitrary criteria. It’d be easy to redesign the criteria to include viruses and it’d be equally valid.
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