Final answer:
Multiple system atrophy is not associated with expansion of trinucleotide repeat sequences, unlike Friedrich's ataxia, Myotonic dystrophy, Fragile X syndrome, and Huntington's disease, which are.
Step-by-step explanation:
The disease that is not associated with expansion of trinucleotide repeat sequences from the options provided is Multiple system atrophy (C). Diseases associated with trinucleotide repeat expansion include Friedrich's ataxia, Myotonic dystrophy, Fragile X syndrome, and Huntington's disease. Multiple system atrophy is a progressive neurodegenerative disorder not known to be caused by such genetic mutations. In contrast, conditions like Huntington's disease exhibit autosomal dominant inheritance, where the expansion of CAG repeats within a gene results in a faulty protein, toxic to neural tissues, and is sufficient to cause the disorder even when only one copy of the gene is affected.