ELi5: How does epigenetics work?

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I get that your DNA can loosen and condense in different areas to allow certain genes to be expressed in higher or lower amounts, respectively. But how do things going on in your environment change how loose/tight your DNA is in specific areas?

And how does your body decide for an area of DNA to be permanently loose or permanently condensed?

And how does this get passed down to your kids?

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Anonymous 0 Comments

So epigenetics is an entire subfield within cell biology/genetics and is also rapidly evolving as more research is done, but I’ll try my best to ELI5 it.

The main way that cells respond to any environmental factor is through signaling pathways. Proteins detect certain stimuli, either within the cell or outside of it, and pass that signal on to other proteins, who pass it on to other proteins, so on and so forth until it reaches a final protein that enacts whatever effect the cell wants to turn on. In the case of epigenetic changes, these proteins can “write” the epigenetic code “on top” of the DNA, thus changing which genes are turned on and off. Different signals will activate different pathways and turn on/off different genes, according to what the cell “wants” to do. (Cells don’t have brains, but it helps to anthropomorphize sometimes)

An important note is that a lot of permanently turned off genes aren’t turned off in response to environmental factors, but because they’re simply not needed in that particular cell type. Bone cells turn on different genes than liver cells, for example. This works very similarly to other changes described above, but instead of environmental signals, the cells are responding to developmental signals (mostly from other cells) while you are still an embryo.

And I’m not super well-versed in the heredity of epigenetic changes, but here’s how I generally understand it: Since the epigenetic code is chemically “written” on the DNA, it can get passed along through the sperm and egg just like the DNA itself. How the sperm and egg “choose” which changes to pass on I can’t say (and tbh we may not even know), but we’re pretty sure it is a real phenomenon separate from genetic inheritance.

I know this is a lot, so if anything is confusing, I can definitely expand on it (to the extent of my knowledge)