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Fenrisvitnir t1_j5htmhk wrote

One method:

(1) We can measure genetic drift rate of DNA.

(2) We can find partial or whole retro viruses encoded in DNA of animals such as humans because they insert themselves during replication.

(3) We can compare the viruses of today to the encoding of the virus in the DNA, and we know the age of the DNA due to the drift rate in (1). We can also therefore determine the age of the virus at time of insertion.

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Another method:

(1) Measure the mutation rate of similar viruses.

(2) Find old instances of the viruses from known prior historic periods.

(3) Compare the RNA patterns to find the mutations.

(4) Calculate the approximate age based on the mutations.

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Many other methods exist, and generally they line up. Reading:

"Yet, over recent decades it has become apparent that viruses occasionally leave a historical record in their host's genomes in the form of endogenous viral elements (EVEs)"

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5962544/

LTR sequence divergence rates:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3048862/

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Ok_Motor_2609 t1_j5ilqal wrote

Do viruses have DNA? Aren't they in between death and life?

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snylekkie t1_j5ilxj3 wrote

Dude. At molecular level there is no life and death. It's just a machine

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ensui67 t1_j5ip6i3 wrote

Well, the question still remains and actually is, if they do not possess the actual machinery for them to replicate, are they actually a complete machine(alive)?

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Perfect-Height-8837 t1_j5iqwa7 wrote

The best way I've heard it described is, they are dead when outside a cell, alive when inside.

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screen317 t1_j5j4x7n wrote

There are tons of cellular obligate parasites that render the discussion moot

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LittleCreepy_ t1_j65t38v wrote

I try to put it into words like this:

A virus can be understood to undergo different developmental stages. Much like an insekt goes from egg to larvar to adult, a virus goes from virus particle, floating alone and, debatably, dead in their environment, to integrating itself into the host. It quite litteraly overlapes with their victim, the cell becomes, to an extend, two individuals rolled into one.

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Silunare t1_j5ipkew wrote

It makes no sense to equate a complete machine to being alive. Also, they do have DNA but not the machinery to replicate, which is why they have to take over cells as replication factories.

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fredmund0 t1_j5ipvq8 wrote

Yes they (mostly) do , this is what they insert into cells to get them to build multiple copies of themselves...

There are exceptions such as (from my memory, it's been a while since I studied) HIV which is a retrovirus, it uses stashes it's instructions as RNA.

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CaptoOuterSpace t1_j5j47wh wrote

At a certain point maybe it's not so useful to think of something as alive or not.

They do have DNA / genetic material. That means, whatever you want it to mean as far as if theyre living?

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hydroxypcp t1_j5j5ern wrote

that's how I see it too. On a molecular level, there are no "alive" tags so where's the line? With things like viruses and prion proteins, it's difficult to argue there really is a reasonable line.

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Classy_Maggot t1_j5jerxt wrote

Yes viruses have DNA, and a protein body to aid in moving around and injecting into a target cell that's it. That's why they're not really quite an alive entity Because there are no self sustaining cellular organs that bacteria and etc have

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Belzeturtle t1_j5jlggx wrote

Some do, some don't. There's a pretty recent well-known virus that doesn't have DNA. Something with a corona in the name. The corresponding disease is COVID-19.

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LittleCreepy_ t1_j65vdm6 wrote

Well, I understood dna to mean genetic basis in the context of this discussion, but yes. There are in fact RNA and DNA Viruses, which can further be divided in coding and non-coding strand (+ and -) based "liveforms".

There are also Prions, proteins that fold others with the same base aminoacid-chain into the same 3D struckture, in a kind of replication.

Viroids are naked, or non protein or membrane, associated chains of RNA, able to infect plants and responsible for some interesting patterns on some flowers.

To complete the picture there are also gigant virus out there, with their own molecular maschinery responsible for about halve of our atmospheric O2.

These are complex little suckers. And I both love them for it and hate them with a passion.

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