This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic and genetic disorders, Subject name: Pediatrics
All of the following diseases are associated with trinucleotide repeat sequence except: 
Select and explain. 
A. Huntington's disease, B. Fredreich's ataxia, C. Myotonica dystrophy, D. Hereditary motor-sensory neuropathy
D: Hereditary motor-sensory neuropathy
Answer: D: Hereditary motor-sensory neuropathy 
Explanation: Rest of the options are associated with trinucleotide repeat sequence. Triple-repeat mutations (Allelic expansion disorders) Due to an increase in the number of nucleotide repeats above a ceain threshold Length of the nucleotide repeat often correlates with the severity of the disease Anticipation: When repeat length increases from one generation to the next, disease manifestations may worsen or be observed at an earlier age. Disease Repeats Clinical features Fragile X-Syndrome CGG Mental retardation, large ears and jaws, macroorchidism in males Myotonic Dystrophy (Chromosome 19) CTG Muscle loss, cardiac arrhythmia , cataracts , frontal balding Huntington&;s disease CAG Affective disorder Spinocerebellar ataxia type 1 CAG Progressive ataxia, dysahria, dysmetria Friedreich&;s ataxia GAA Progressive ataxia, dysahria , hyperophic cardiomyopathy Ref: Nelson textbook of Medical Physiology 21st edition Pgno: 647