I am an acid, found in all of your friends.
I tell you how to look, but I don't make amends.
My man named Fred, he told you who I am.
But no one understood me until I had an exam!
I've only got one vowel to my name, for sure.
But write me out the long way and you'll find a lot more.
Shout out to my people A, G, C, and T!
All of your bases are belong to me!
Who am I?