What is meant by "single-step mutation"?

[Jamus]

Googling the term above did not help. Can anyone possibly explain the concept to me? Thank you

Jamus

[jonmoulton]

"Single-step mutation" is not a common usage. I'll give a shot at this, but don't just accept this answer, try to confirm it. It would be nice to see the usage in context.

Compare two alleles, a wild-type allele and an allele considered a mutant allele. The mutant allele might have single point mutation. Alternatively, the mutant allele might carry a single rearrangement, such as a small inversion. In either of these cases, only one change is required to get from the gene sequence of the wild-type allele to the gene sequence of the mutant allele. I think this is likely what is meant by "single-step mutation". Sometimes a mutant allele might have several changes from the wild type allele, such as the combination of a small inversion and a point mutation. This would not be a single-step mutation, as it requires two distinct sequence changes to turn the wild-type sequence into the mutant sequence.