Slipped-mismatch chromosome pairing may produce deletion / duplication mutations

     Recall  Holiday-Whitehouse Model of DNA recombination (animation)

    Consider a pair of chromosomes, each with a (CAG)4 repeat

    Suppose repeat regions of homologous strands align "out of register"

    Recombination at the "nick" produces a  (CAG)6  and a  (CAG)2 chromosome

Further slippage in the (CAG)6 chromosome may lead to chromosomes with multiple (10s ~ 1,000s) of repeats.

All figure & text material 2013 by Steven M. Carr