[js1138]

DNA is a language written in 4 letters. That means that for every double mutation (where a gene mutates twice), there should be roughly a 1 in 4 chance of the mutation being reversed. Do they take this into account?

I get one in 16, unless there are "words" that can't occur.

[js1138]

That's from computer background. I know nothing of molecular biology.

[Condorman]

I get one in 16, unless there are "words" that can't occur.

I'm not sure that's correct either. We have not accounted for deletions, duplications, etc. A mutation can be more than just changing a single letter.