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qwertyuiiop145 t1_izhh967 wrote

It’s possible that some bacteriophages (viruses that infect bacteria) are important for keeping gut bacteria in check, though it might be hard to prove that one way or another.

Alternatively, there are parts of the human genome that are theorized to have originally come from viral DNA, so if you count those as viruses still, they are very essential.

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KnoWanUKnow2 t1_izisz5i wrote

It's actually crazy how much viral DNA has been absorbed by the human genome. Roughly 4% of our genes actually code for something, so 4% of our entire genome is what's necessary to make a human being.

8% of our genome comes from viruses. That's double what it takes to make a person. And since it takes a lot less DNA to make a virus than it does to make a human, that's a whole lot of viral DNA.

None of it codes to make a virus anymore, that replication feature has been deactivated. A lot of it is just "junk DNA" that doesn't do anything. But some of it is necessary for human survival.

As an example, we are mammals only because of viral DNA. An early proto-mammal absorbed some DNA from a virus. That virus originally caused nearby cells to fuse together to create a wall around itself which blocked the white blood cells from finding it. That virus no longer exists, but it's DNA got absorbed into the germ cell DNA of it's host and passed along to it's offspring. 200 million years later that DNA is used to create the placenta, which is a fused cell wall that allows nutrients to pass from the mother's blood to the childs, but blocks the mothers immune system from finding and attacking the child. It's what all mammals use to feed and protect their fetuses. It's what allows live birth to happen. So the only reason why humans don't lay eggs is because we absorbed some viral DNA.

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cremasterreflex0903 t1_iziwz8c wrote

You guys don't lay eggs?

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Fo0master t1_izjcwc2 wrote

The whole "4% of our genes are necessary" thing is a bit outdated. It's like saying you only need the tires to make a car because they're the only part that actually touches the road. The rest of the genome still plays a crucial role.

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emelrad12 t1_iznujld wrote

Kinda, it reminds me of neural networks which can be compressed sometimes by 90% and still work fine. Most of the dna is rube goldberg machine.

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MentalUproar t1_izjzh7l wrote

Has there ever been an attempt at creating a “pure” human, either by removing nonessential DNA fragments or building the genome from scratch?

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KnoWanUKnow2 t1_izk4jwb wrote

Humans? No. For ethical reasons there probably never will be.

But they have done it with other things such as bacteria. They've even created an entirely new organism by creating DNA from scratch with just a few genes and inserting it into a bacterial cell that had it's DNA removed.

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[deleted] OP t1_izkwpm5 wrote

[removed]

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Iama_traitor t1_izl93ek wrote

OP isn't exactly correct, there is coding and noncoding DNA. Coding DNA makes proteins, noncoding DNA doesn't, but it plays the vital role of gene regulation and expression, codes for all the RNA produced in our cells, and includes all the introns for coding genes. So you can't live without noncoding DNA.

However, there are plenty of paradoxes that first arose, like how closely related species have vastly different genome sizes. Turns out they had roughly the same number of genes, just huge variation in repetitive DNA. So, along the lines you were thinking of, if there's even a .00001% error rate of transcription or mutation and all of your DNA was 100% necessary for survival, there's no way you could survive or reproduce. So large genomes actually end up requiring more and more repetitive DNA to hedge the odds.

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Neither-Situation t1_izljcmf wrote

In information theory they talk about channel capacity, which sets hard limits on how much information can be transmitted. Is there much knowledge on these limits in DNA coding? can it be different in different organisms, as obviously some lifeforms having a much more restricted range of bodily functions and chemicals available compared to large mammals say.

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JackJack65 t1_izhnzja wrote

It's true that a significant part of the human genome is made up of endogenous retrovirus sequences. Retroviruses are a special type of virus that can integrate into the genome of its host (HIV is an example). In the ancient past, human ancestors were apparently exposed to a lot of retroviruses and probably many died as a result. Sometimes leftover fragments of retroviral genes got stuck in our genome, and as a result began to evolve cooperatively with our genes (or competitively, in the sense of transposons duplicating themselves).

In HIV-negative humans, there are no functional retroviruses left in our genome, so these aren't considered full viruses anymore, just leftover pieces. Some of these endogenous retroviral genes have since evolved important functions that benefit us, and viral infections were likely an important driver in generating novel, functional genes in our evolutionary history.

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JackJack65 t1_izhln6v wrote

No, viruses aren't required for humans to stay alive. Viruses often kill the cells they infect, and at no point does the body depend on viral infection for normal development.

That said, in practice, there are some viruses that nearly every human gets exposure to, that are considered desirable to get exposed to at a young age (to avoid complications of getting exposed at a later point in time). Cytomegalovirus, for example, does not cause severe disease in young people when they are exposed, and the body has the chance to build up antigen-specific immunity, but if a woman is exposed to cytomegalovirus for the first time during pregnancy, this can have serious complications for the developing child.

Likewise, the five endemic human coronaviruses (OC43, NL63, HKU1, 229E, SARS-CoV-2), influenza A virus, varicella zoster virus (which causes chickenpox), are so widespread that there is a virtual guarantee that you will be exposed at some point during your life, therefore it is important to develop antigen-specific immunity to these (ideally by vaccination; ideally when you are young and healthy) to avoid the dangerous complications that can occur, especially if you are exposed for the first time at an older age.

At any given point in time, there are always billions of bacteriophages replicating inside you. Bacteriophages are viruses that infect bacteria and are widespread throughout the whole world. The human digestive tract is sterile at birth, but is quickly colonized in the first few days of life by bacteria that bring bacteriophages with them. Bacteriophages cannot infect human cells, so their effect is primarily on their bacterial hosts, not us directly. (Humans can survive and develop without gut bacteria if they are kept in sterile conditions, so in no way are these bacteriophages essential for human life.) Since most of the bacteria in your body is in your gut and on your skin, bacteriophages may play a role in killing some bacterial families allowing other types of bacterial families to fluorish, which could be good or bad, depending on the situation, something scientists have tried to harness to combat dangerous bacteria (with something called phage therapy).

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mayonnace t1_izij5s5 wrote

Don't know about humans, but I've recently read that some species of wasp have genes to produce specific type of virus in their ovaries, which, when they inject their offspring into host's body, the virus infect the host to suppress their immune system, so the offspring stays safe. A parasitic system using or supported by another parasitic system. Amazing.

In case you don't know, apparently, some species of wasp inject their offspring into some caterpillars, which then come out of the host's body as larva by piercing through their skin or something. I guess stuff like this is what inspired Alien movies.

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Torturedballsack14 t1_izs2sro wrote

Yes. We actually live in a symbiotic relationship with some viruses, they are a part of our microbiome and safeguard our health.

Bacteriophages are viruses in our guts that eliminate harmful bacteria, this also gives the ability to be used as a alternative antibiotic.

Viruses may also have indirectly propelled evolution throughout time. Virus fighting proteins such as the APOBEC proteins may have triggered multiple genetic explosions that have helped sculpt the modern in human.

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