# How can all DNA be encoded with four molecules?

Only four nucleotide 'bases' make up the code for all life...
08 October 2019

## Question

How can we encode all the instructions in our DNA with only four molecules?

Phil Sansom shed some light onto this 'basic' problem...

Phil - It's a good question, because there really are only four molecules at the most fundamental level. They're the four nucleotides and between those four, obviously billions of those four, but that makes up all life as we know it. Now four doesn't seem like that many, but to be honest it's actually two more than all computers use, all the stuff that Beth here has been talking about, which is just ones and zeros right. That's only two components of your code. So actually for especially when you consider how many of them there are, maybe that's all right to have like, such a small set of fundamental units.

Now there's another question here, which is: Why four? Why not two? Why not six? Why not five or three for example? That's still up in the air but there's an interesting theory that came out a couple decades ago in a research paper which relates to something called a Grover Search. Now a Grover Search is a mathematical concept that uses quantum mechanics to determine a way to search a given set of options for one that you're looking for. With this Grover search that uses the quantum effects, you can search through a number of options in fewer steps than if you weren't using quantum mechanics. Now the reason this is relevant to DNA is if you're doing a 1 step Grover search then the optimum number of things to search between is four, if you're doing a three step Grover search the optimal number of things to search between is 20. Now that's kind of weird because there's three nucleotides and those nucleotides code for amino acids and there's actually 20 amino acids. So in this paper that came out a couple decades ago someone was like: “Hmmm? Interesting?”

Phil - Spooky. The numbers are the same. Perhaps when these molecules or these things that whatever, are searching through nucleotides to find the right one, or searching through amino acids find the right one, maybe they're using this Grover search with these quantum effects and that's the reason that these numbers, four and 20 exist in nature. Not definite science but could be cool. Look out for that one.