How Much Information Is in DNA?
29th March 2026
Do you like information theory? Do you like molecular biology? Do you like the idea of smashing them together and seeing what happens? If so, then here’s a question: How much information is in your DNA?
When I first looked into this question, I thought it was simple:
Human DNA has about 3.1 billion base pairs.
Each base pair can take one of four values (A, T, C, or G)
It takes 2 bits to encode one of four possible values (00, 01, 10, or 11)
Thus, human DNA contains 6.2 billion bits.
Easy, right? Sure, except:You have two versions of each base pair, one from each of your parents. Should you count both?
All humans have almost identical DNA. Does that matter?
DNA can be compressed. Should you look at the compressed representation?
It’s not clear how much of our DNA actually does something useful. The insides of your cells are a convulsing pandemonium of interacting “hacks”, designed to keep working even as mutations constantly screw around with the DNA itself. Should we only count the “useful” parts?
And that’s just your nuclear DNA. Your mitochondria have their own DNA, a relic of the independent microbe that they were before being symbiotically fused with eukaryotic cells.