(A) Scaled mutation rates, (1/μ)β(i, ŝAC) for pure AC repeats (shaded line) and (1/μ)β(i, ŝiAC) for once-interrupted iAC repeats (dashed line), as a function of repeat length under the PL1 model. (B) The rate ratio β(i, ŝAC)/β(i, ŝiAC) as a function of repeat length i.