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KnoWanUKnow2 t1_izisz5i wrote

Reply to comment by qwertyuiiop145 in Are there any viruses that humans must have in/on our bodies in order to stay alive? by [deleted]

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The whole "4% of our genes are necessary" thing is a bit outdated.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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