Tri-nucleotide expansions in human neuro-muscular disease

    Trinucleotide repeat diseases were unsuspected prior to investigation of Huntington Disease. They are now known to be quite common: CAG expansions are implicated in a number of neuro-muscular conditions, where the consequent poly-Glu repeat within the translated product produces plaques that interfere with normal function. Expression of the modified protein therefore 'dominates' the standard product: the allele behaves as a dominant.

Figure © 2012 TA Brown, Introduction to Genetics (1st ed.); additional text © 2014 by Steven M. Carr