Figure 8.Variation in the polyglutamine stretch encoded by the (CAG)nCAA repeat in exon 1. The normal range of this stretch is 9 – 38 glutamine residues, while in the motor neuron disease spinal/bulbar muscular atrophy (also called Kennedy’s disease) the (CAG)nCAA repeat in exon 1 is expanded and codes for more than 40 Glutamine residues.