How does genetic memory work?

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How does a baby bird know to act like a poisonous worm when a predator shows up? The answer is genetic memory, but how does it work? How does it get encoded into dna, passed down, and executed.

In: Biology

There’s not a super direct answer to this because we don’t know everything about nervous systems (i.e., the brain, brain stem, peripheral nerves). But the basic answer is that the “memory” isn’t for a specific behavior. It’s for specific proteins and configurations of proteins and stuff like that.

An analogy is a book having “memory” of a story. It doesn’t actually. It’s just a bunch of shapes. The shapes are a code that have to be decoded through the process of reading. Then you get the story, despite each individual code only being a single, simple word.

Similarly, DNA has codes for proteins. Individually, they’re useless, just like if all I sent to you was the letter Y with nothing else. If you read them wrong (errors in making the proteins and stuff), they’re useless, like sdjalkdfs. But in the right sequence, you get a bird that wiggles like a worm.

Why did that sequence become common? Evolution. Those are the birds that survived and reproduced. So they’re the ones who stuck around for you to see today.

How do new complex behaviors emerge from DNA memory? Mutation and some other stuff I forget at the moment. The behavior may have been less notable at first. And over time, evolutionary pressure “selects” the most worm-like bird behavior.

Oh yeah, once the brain is whole and “on,” the animal can learn, too. So sometimes the behavior is just a predisposition to learning a specific thing. Like humans are predisposed to learn language.

Super interesting question. I’m sure as animals us humans also have genetic memories. Hope many can shed light on this topic.

It might be more accurate to say the baby birds have instinct, rather than genetic memory. Memory implies learned behavior, while instinct is behavior that stems from evolution.

At some point in time a baby bird had a genetic quirk that cased it to act somewhat similar to a poison worm. Predators found this off putting (either though learned behavior from a previous encounter with a real poison worm, or instinct of their own). Those baby bird lived to grow up to be adult birds, who had quirky children of their own. Over time that behavior became refined like only acting wormy when predators are around, acting extra wormy, etc.

It might help to look at what our own instincts “feel” like. For example, how do you know to eat food and not to eat mud? It’s probably a universal thing for people to try eating dirt, mud, etc. as a child, but outside of a few cases, this is something you do not make a habit of. Things like the flavour tell us mud is bad. Why is it bad? Because it tastes bad. Why is food good? Because it tastes good (at least most of it, some can be hit or miss).

But flavour isn’t an inherent quality of materials. It’s purely in our minds, caused by taste receptors on our tongue reacting to certain molecules. The tastes considered “good” are tied to the presence of certain molecules, and vice versa for bad. The end result is that we “know” to eat food without specifically having to be taught.

This connects to genes because the instructions for how to make taste receptors are encoded in DNA. Variations in the exact shape result in different preferences, such as the same food tasting pretty good to one person, but terribly bitter to another.

>How does it get encoded into dna, passed down, and executed.

You’re thinking of it backwards. Things didn’t start “outside” the DNA and then get encoded into it. Things start as DNA and then the DNA makes us, who do things.

As for how DNA is passed down and used, there’s a wide variety of educational videos and articles meant to teach this topic. [Crash Course youtube series](https://www.youtube.com/watch?v=CBezq1fFUEA&list=PL3EED4C1D684D3ADF&index=11) and [Khan Academy article](https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/transcription-and-rna-processing/a/overview-of-transcription). If you have further questions, do not hesitate to ask!

to OP: Although this isn’t an answer: There is also evidence that experiences can be passed down through DNA. Although the evidence is scant and not clear, there have been some studies to suggest if you expose an animal like a rat to a stimulus (like a little red room) every time that it eats, that it’s offspring will salivate more when exposed to a red color vs. a control group.

But, we totally do not understand the mechanism behind this.

This is something pretty difficult to ELI5 because the answer involves a lot between DNA and behavior and a lot of that is not well characterized. Every answer is bound to be fairly badly incorrect (for instance, those asserting that it is NOT memory are probably, to some degree, incorrect – and, in fact, contrary to what we were all taught – Lamarck was not entirely wrong either).

Some DNA is transcribed into RNA which is translated into proteins. Not all DNA is used to encode proteins.

DNA, RNA, and proteins all control when and how much any given protein is produced. The when is important. Producing certain proteins at specific times can determine what kind of cell the cell is.

When birds (or people or dogs or any complex multicellular organism) are developing from a single cell protein expression for various cells are turned on and off. This varied protein expression allows different kinds of cells to be produced from a single cell (the bird egg).

Some of those cells are brain cells.

Differential expression of proteins also produces architecture in the brain of the bird. The bird’s brain is not homogeneous with every cell and its interactions with other cells identical.

Some connections between some cells in the brain are, in fact, determining the observed behavior. Those connections were formed early in the bird’s life and were most likely created by differential expression of proteins.

It is NOT certain at all that the differential expression of the proteins that leads to the brain architecture storing the behavior is directly encoded in the DNA. Some part of it likely is and some part likely is not. Some part may have arisen through mutation and some part may have arisen through what used to be called Lamarkian evolution – and now is called epigenetics.

That’s all probably not ELI5 but what you are asking is simply not fully characterized. My suspicion is that you are, in fact, correct to call it memory because I suspect that when neuroscience fully characterizes complex brains we will find that memory and innate behavior are not nearly as different as some assert. They are almost certainly not the same but IMO they share many similar and some identical methods of encoding.

There’s no memory, you have the cart before the horse. Let’s say you’ve got a gene which makes your neck twitch, and you’re therefore constantly instinctively and involuntarily looking in different directions as a result. That behavior causes you to spot a predator before you’re killed, and therefore you survive to spawn offspring and pass on that trait. Genes don’t learn, they only change at random, and the random ones changes which benefit the organism will help that organism outlast random changes which do not.