Microsatellite evolution: Markov transition functions for a suite of models

This paper takes from the collection of models considered by Whittaker et al. [2003. Likelihood-based estimation of microsatellite mutation rates. Genetics 164, 781–787] derived from direct observation of microsatellite mutation in parent–child pairs and provides analytical expressions for the probability distributions for the change in number of repeats over any given number of generations. The mathematical framework for this analysis is the theory of Markov processes. We find these expressions using two approaches, approximating by circulant matrices and solving a partial differential equation satisfied by the generating function. The impact of the differing choice of models is examined using likelihood estimates for time to most recent common ancestor. The analysis presented here may play a role in elucidating the connections between these two approaches and shows promise in reconciling differences between estimates for mutation rates based on Whittaker's approach and methods based on phylogenetic analyses.