  Suppose a finite set $X$ is repeatedly transformed by a sequence of
permutations of a certain type acting on an initial element $x$ to produce a
final state $y$. We investigate how 'different' the resulting state $y'$ to $y$
can be if a slight change is made to the sequence, either by deleting one
permutation, or replacing it with another. Here the 'difference' between $y$
and $y'$ might be measured by the minimum number of permutations of the
permitted type required to transform $y$ to $y'$, or by some other metric. We
discuss this first in the general setting of sensitivity to perturbation of
walks in Cayley graphs of groups with a specified set of generators. We then
investigate some permutation groups and generators arising in computational
genomics, and the statistical implications of the findings.

Quantitative Methods;Discrete Mathematics;Populations and Evolution