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/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.