system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Genetics and DNA

I've read recently about fears of immunizations affecting DNA. I understand that this is not the case and that the injection is "Genetic Material" to give instructions to your body to replicate certain things.

What I don't understand is: Your genetics affect your future children; so by introducing genetic material aren't you changing the DNA of future humans? 

If in fact this is the case isn't it possible that you won't see side effects of these injected materials until the next generation is born?
gpt
DNA lives in the nucleus of your cell.  It makes mRNA, which is basically copies of the DNA (it has some structural differences), but in little snippets.  The mRNA goes out of the nucleus, and is used as a blueprint to build the proteins that particular genes code for.  mRNA does not get incorporated into the genome.  It doesn't change your DNA.  It isn't inherited.

Think of it like a library full of cookie recipes.  DNA are the actual recipe books.  We keep them locked up in the library so people don't fuck them up.  You can go in and get photocopies of specific pages and take them with you.  Those mRNA.  You use the information on those pages to make cookies (proteins) at home.  The photocopies are made out of really weak, crumbly paper, and your body will break them down over time.  The proteins they made will eventually wane too.  The library books themselves remain unchanged.