"No. No. There are four kinds of nucleic acids. I can’t remember what they
are, but there are four kinds. But there are... billions of
combinations," he guessed. "Billions. And how they are arranged is what we are.
It’s like a pass code. If you have ‘one,’ ‘two,’ ‘three,’ ‘four,’ and the pass
code has fifteen slots, then you get to arrange the numbers in those slots. 
That’s the combination for that lock. You and me, we’ve got these billions of
slots, and how our four acids are arranged, those are our combinations. That’s
who we are."