<prompt> Which of the following is not caused by over expression of a trinucleotide repeat?Alzheimers diseaseFragile XHuntington diseaseSpinocerebellar ataxia Type 2  <response>: Ans: a Alzheimers disease Ref: Ganong, 22nd ed, p. 215Alzheimers disease is not caused by over expression of a trinucleotide repeat. The rest 3 options are examples of trinucleotide repeat diseases where as Alzheimers is primarly a degenerative disease Basal ganglia resulting in movement disorder.Some examples of trinucleotide repeat diseases:-Huntingtons disease -- CAGSpinocerebellar ataxia --CAGType 1, 2, 3, 63Fragile X syndrome -- CGGMyotonic dystrophy -- CTGFrederichs ataxia -- GAA 