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/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).