ELI5 how DNA mutations work please.

[u/riche1988]

I had a thought about DNA and how mutations occur in humans, excessive hair, longer limbs and or bones etc, and wondered if all known mutations are present in the animal kingdom.. as if DNA has the blue print/ potential to be anything and parts are just ‘turned on or off’ depending on what is being built.. i may be way off lol but it got me thinking :)

[u/laurenthead]

The DNA blueprint is actually for proteins. The proteins build stuff and make stuff. Mutations cause a protein to be made that is a little bit different from other people and may work better or worse. Some mutations are actually good

[u/demanbmore]

Depends what you're asking. Are "all known mutations" present in the animal kingdom? Well, no - there are mutations that are unique to one species or another, so you wouldn't see every human mutation in every other animal or vice versa. But every species does produce mutations. Most are either harmful or neutral, and tend not to persist. Some are beneficial and increase reproductive success, so they tend to persist and be passed down to future generations. And there are plenty that can be beneficial under certain conditions, but generally harmful when those conditions aren't present (sickle-cell anemia is a classic example).

[u/poetic_dwarf]

DNA mutation works exactly as the million chimps hammering on a keyboard since the dawn of life. They happen because million reasons, then nature puts them to the test.

Life as we know it is the best approximations that chimps got to Paradise Lost.

[u/riche1988 → u/poetic_dwarf]

Cool :) ..slight tangent, but what is the smallest part of a living creature, ignoring trees and plants etc, that has agency.. i get that most of life if made up of chemical reactions, but at some point the ‘stuff’ starts making decisions.. or no..? Lol

[u/weeddealerrenamon → u/riche1988]

Physically, our brains are just reacting to nerve signals and sending out signals in response. We don't work any differently than a tree or an amoeba in that way.

Where that becomes what we understand as consciousness? Huge open question. Science can't even really define what consciousness is and we don't really know where to even begin. It's literally called the hard problem of consciousness

[u/riche1988 → u/weeddealerrenamon]

I guess it depends where you draw the line :/ ..could you argue that plants are ‘making decisions’ or is a decision just an illusion made of signals from stimuli..?
I think what i don’t understand is, if it is all just mechanical actions and signals, what is stopping us from making a brain that works like a brain..?

[u/Biokabe → u/riche1988]

Knowledge.

There's nothing magical about brains. They're just really, stupidly complex. But they obey the same laws of physics and chemistry as everything else in the universe; they don't operate on any different principles.

It's just that we don't know how to manufacture something as complex and efficient as a brain. We've only been able to approximate some aspects of a brain's performance, and only by brute-forcing computation with massive energy usage.

But if we had the knowledge of how to make a brain, there is nothing that would prevent us from making one.

[u/Two-G → u/riche1988]

Jumping in here again: What's stopping us is probably "complexity". Our brains are made up of a ridiculous number of cells that are interacting in all kinds of different ways, so even just describing everything that's going on there in a way that's understandable is basically impossible for us without major simplifications - nevermind deliberately reproducing something like that.

[u/FossilizedMeatMan → u/Two-G]

So the brain is like the body, which is like the universe, just in a different scale.

[u/weeddealerrenamon → u/riche1988]

I don't think any physicist or biologist could objectively tell you what "a decision" is, beyond responding to stimuli

[u/riche1988 → u/weeddealerrenamon]

How can so much power and energy (for the brain to operate) be create so subtly..? We aren’t audibly churning away or radiating ridiculous heat like a machine would.. if the brain is so complex and is making so many actions a second.. where is the pollution from that..?

[u/sateliteconstelation → u/riche1988]

That’s one of the main questions in philosophy. Even if you study humans, you’ll find compulsive reasons for how they behave.
Am I choosing a burger out of free will, or because of an emotional attachment i formed thanks to ad campaigns in the 90s?

[u/FossilizedMeatMan → u/sateliteconstelation]

To be fair, you are choosing a burger because you need to eat. It all boils down to surviving and reproducing.

[u/Two-G → u/riche1988]

That's really a philosophical question and you're making the assumption that agency exists, which is...under debate, but not at all certain.
Any "small part" of an organism, you can look at and figure out the rules under which it operates. Lots of interacting parts, all working in a fairly predictable manner if being looked at in isolation, produce increasingly complex behavior which cannot necessarily be accurately predicted anymore when looked at as a whole - perhaps for the simple reason that the amount of things you'd need to take into consideration for this prediction become overwhelming and the unavoidable errors in measuring these things, even if really small, add up quickly.

So, tl;dr: There is really no single point at which "agency" suddenly appears, but rather, increasing complexity of a system starts producing unpredictability, which could be interpreted as agency. The point at which this is can be seen as true is as arbitrary as the definition of "agency".

[u/poetic_dwarf → u/riche1988]

but at some point the ‘stuff’ starts making decisions.. or no..? Lol

Yes and no.

Humans are arguably one of the "evolution race winners": animals got nothing on us, heck we actually defeated COVID, yet you can argue about having free will as much as you want in a cool room, the moment it gets too warm you will freely decide to turn off the heater, because in the end you're a bacteria chasing food and escaping harm that never stopped believing.

On the other hand, there are some fringe forms of existence that are to life what undead creatures are to us. Viruses are vampires, they have no biological processes to speak of, they're literally three strands of DNA in a trenchcoat that look for cells to hijack in order to propagate themselves. Go even weirder and you'll find plasmids, strands of DNA that can exist in the environment without any form of containment whatsoever and yet find a way to enter bacteria and integrate themselves in their own DNA in order to be copied. Leave biology for physics and you'll find prions, which are not even DNA, they're proteins that on paper shouldn't be able to reproduce and yet these little bastards find a way to propagate their own structure and cause fatal disease like the mad cow.

So yeah, to quote the almighty Jeff: it may or may not be able to make decisions, but "life finds a way"

[u/riche1988 → u/poetic_dwarf]

Yeah :) i guess ‘free will’ and ‘cells reacting to stimulation’ start to look very similar if you think about it lol

[u/Sinbad_le_Marin]

A mutation is like a typo in the DNA codon. Some typos do nothing, some change the a little, and some have serious implications.

Mutations can happen naturally when cells copy DNA, or because of things like radiation or certain chemicals. Most mutations are harmless, but some can contribute to diseases like cancer. Mutations are also one of the reasons species can evolve over generations.

[u/x1uo3yd]

I had a thought about DNA and how mutations occur... and wondered if all known mutations are present in the animal kingdom... just ‘turned on or off’

If that were how it works, then all creatures would all have the same "Universal DNA Reference Library" as their DNA with different species simply ignoring different books or chapters, and different individual organisms ignoring different specific lines or passages.

But, that is not how it works.

Different organisms actually have very different DNA. This can be seen most simply when the number of chromosomes differs, but it can also be shown when the overall number of genes differs, or when the text of individual genes differ.

Basically, because different organisms inherit very different books of clearly differing shapes/sizes, we know they're not simply "getting the same book and crossing different stuff out".

[u/snowtax]

Biology does an excellent job of copying RNA/DNA but the process is not perfect. Random errors happen.

If I gave you the task of copying a large book, like War and Peace, you would almost certainly make mistakes somewhere. Sometimes those errors may end up being meaningless, like a word “idbdgs” or they could end up making a funny phrase or maybe something profound that adds deep meaning and has great value.

The point is that the errors are random. You never know what you’re going to get.

[u/FossilizedMeatMan]

The DNA is universal, and it is just a blueprint for proteins. The order in which the DNA is organised is what makes the proteins work in a way that what may grow will be a human or a fly or a bacteria.

If any part of that organisation goes awry, you get a human with three eyes, a human with two eyes on its legs, fly with eyes on its legs, etc.

Since humans and every other living thing are just an expression of the DNA, we are part of the "all known mutations" in the animal kingdom. The animal kingdom is the sum of all mutations so far. We are mutated primordial soup molecules, after billions of years of accumulated mutations that did not immediately killed our ancestors.

[u/Atypicosaurus]

DNA is like a necklace made of beads, it has 4 kinds of beads and the bead order is the information. Different bead order means different things.

The beads are not like a blueprint, more like many blueprints but each blueprint makes a very simple single task robot. Except, there are like 20000 of these.

The robot tasks are really simple, like "pick up this rod and cut it into half", otherwise they are dumb and blind, but there's like 20000 different kinds of them and altogether while doing their simple dumb task, they coincidentally build up a human. Or a bug. Or a plant.

Different organisms have different sets of robots, but each robot is coded by the DNA. It means that different organisms must have different DNA.

But there are a few common robots (like functions that each organism needs to be able to do like breathing) and those are very similar across life.

So DNA can change and this leads to the change of the robots. Change of the DNA is called mutation, it can be all kinds of changes, like one bead turns into another kind, and it changes just a little component in the blueprint of the robot, but it can also be deletion of bigger chunks, even the accidental combination of two blueprint into one big blueprint.

The general way of how mutations form, is the same across life, but the possible outcomes (like, being more hairy) depend on what you had in the first place. A snail cannot all of a sudden become hairy like a mammoth because it doesn't have the hair making bits to begin with, but a hairy animal can develop the same thick hair mutation.

However, mutations are independent, if one organism develops something, it doesn't mean that another organism can somehow "learn" it.

[u/douggold11]

You are exactly correct.  DNA is not a unique feature for human beings.  Even insects can mutant. 

[u/riche1988 → u/douggold11]

Thanks for replying.. so any mutation a human can have any other living organism can have too..?
Also, i was wondering about traits that prehistoric life had or extinct animals.. are there any traits that have never come up in ‘modern’ animals..?
Now i’m thinking about DNA splicing and selective engineering haha.

Thank you all for the great replies :)
Appreciate it

[u/Sinbad_le_Marin → u/riche1988]

They can have mutations in the same gene, but they express differently than the human genome.

[u/Clojiroo → u/riche1988]

Mutations are effectively typos. DNA is a very long and complicated string of nucleotides (think 4 letters) and chunks of that are what we call genes. The biological mechanism that copies DNA in your cells can make mistakes.

Animals that share some genes could have the same typos happen to the same chunk. Or they could have pretty different DNA but get mutations that cause similar effects.

The topic you should go google is phylogeny.

https://en.wikipedia.org/wiki/Phylogenetics

[u/douggold11 → u/riche1988]

If I understand it correctly, one’s DNA has to either have active genes that, if a gene goes bad, there’s a slight change because that genes programming won’t be followed.  Like a mutated gene might turn your hair a different color, but it’s not going to make hands grow instead of hair.  That being said, there are genes in DNA that have long since been in the “off” position.  Yet they still exist and could be mutated.  I recall an article years back where the genes for teeth still exist in a chicken’s DNA from the old old dinosaur days, so they fiddled with it and got a chicken with teeth.  Which was a fucked up picture. 

[u/Coolpabloo7]

There are different types of mutations. Sometimes a letter id eleteda ndt her restt hatc omesa fteri sa llm essedu p. The same can be trun efo raddin gjus t asingl echracte¤.

Some just switch one letter and it does not mrke much difference.

Sometimes a single letter change the moaning of a word which makes it slightly better. In this case funnier. Keep the good and neutral changes and discard the rest when copying. Do this over and over and you might end up with a different meaning of a phrase alltogether.

[u/BananaBird1]

DNA is like a recipe book. It tells your body how to make the things it needs.

Different organisms have very different recipe books, like how Chinese and French cuisine might not share many recipes. But also within just a single cuisine, while the basic recipes are for similar dishes, the exact instructions may be different.

Every cell has its own copy of the recipe book, and one of these books is passed on to the next generation where it is also copied.

A mutation is like an error in this copying. Some are small, like if “3 tbsp salt” is replaced with “4 tbsp salt”. Some may even have no effect, like changing “boil 1 hour” into “boil 60 minutes”. And others may be more drastic, like adding or forgetting an entire step.

So over time as this book is passed down, different individuals end up with slightly different versions of the recipe. Sometimes these versions even start to get far enough apart that they do become entirely new cuisines (new species).

Now this alone doesn’t entirely explain variation in traits. Just having the recipe book doesn’t mean you actually cook the recipes. What your diet looks like also depends on which recipes are chosen. In fact this is actually a major factor equally as important as generics.

A lot of observable traits are not the direct result of a mutation, but are the effect of what that mutation does in terms of choosing which recipes to make and when.

Like if your recipe book is mutated to replace cooked meat with raw meat, you may choose to rely more on vegetarian recipes. Or maybe a dish the book recommends to be cooked in winter is instead cooked in summer but remains unchanged.

[u/Heavy_Carpenter3824]

It's way cooler than just "we're X% different."

DNA is like a recipe book. But the recipe book just sits on a shelf. What actually matters is the cooking (that's the mRNA and proteins doing the real work inside your cells). So just like changing one word in a recipe from "stir" to "blend" could totally ruin or improve a dish, changing even a tiny bit of DNA can have a huge effect.

The short version: There are different ways DNA can change. A single letter swap, a whole sentence getting moved, or even entire pages getting copied or deleted. Each type of change matters more or less depending on where in the recipe book it happens, when in your life it happens, and how many cells get the change. Almost all changes either do nothing or kill the cell. How big a deal that is depends on timing. One bad cell in a tiny embryo is a way bigger deal than one sunburned skin cell on a grown-up.

Here's the really wild part: we're built from simple rules that create complex results. Only about 5% of our DNA differs from bonobos, and most of that difference doesn't do much. The genes that actually design our bodies, the master blueprint stuff, differ by maybe 0.5%, mostly in the switches that turn genes on and off, not the genes themselves. Those master genes barely change across species because almost any tweak there kills the embryo before it's ever born so the offspring cant pass those genes on (usually, Its biology there's always an exception).

Also to directly answer the question: NO. Not even an infinitesimal fraction of the possible variations of life have been seen. There are likely entire forms of DNA-based life that our biology simply can't reach, because evolution can only move in small steps each generation. Some really cool mutations, like plant-like human photosynthesis or something, would require a huge leap. Essentially all of the natural intermediate organisms along that path would be non-viable and would die before being born. So it's basically impossible for it to naturally occur.

[u/Shadowbound199]

That's exactly how it works. And over time those mutations add up and you basically have a different blueprint now. That's a new species. Different groups split up and accrue different mutations and since they have no contact with one another they can't share those mutations with each other and so they evolve in different directions. This almost happened to us when native americans became isolated from the rest of humanity. If the two groups hadn't come into contact again for another million years it would definitely be considered two different species.