Dr. Carpenter: Agent Scully.
Scully: Oh, Dr Carpenter, I fell asleep.
Dr. Carpenter: I've done some work. These are the DNA sequences from the bacteria sample you brought in. You seem to know something about molecular biology. Do you know what you're looking at?
Scully: Yeah, I think these are genes.
Dr. Carpenter: Right. They're called base pairs. Each pair is made up of something called a nucleotide. Only four nucleotides exist in DNA, four. And through some miracle of design that we have yet to fathom, every living thing is created out of these four basic building blocks. What you're looking at is a sequence of genes from the bacteria sample. Normally, we'd find no gaps in the sequence. But with these bacteria we do.
Scully: Why is that?
Dr. Carpenter: I don't know why. But I tell you, under any other circumstances my first call would have been to the government.
Scully: What exactly did you find?
Dr. Carpenter: A fifth and sixth DNA nucleotide - - A new base pair. Agent Scully, what you are looking at, it exists nowhere in nature. It, would have to be by definition... extraterrestrial.