A 5-Year-Old Boy Is Being Evaluated for Progressive Muscle Weakness

question 87

Multiple Choice

A 5-year-old boy is being evaluated for progressive muscle weakness that has resulted in numerous recent falls.  There is no family history of muscle disorders.  Physical examination reveals bilateral calf enlargement.  When the patient is asked to stand, he uses his hands and arms to help push himself to an upright position.  Serum creatine kinase is 12,600 U/L (normal: 30-170 U/L) .  Molecular tests reveal a large muscle protein that is defective due to the loss of 508 amino acid residues.  Genetic analysis reveals a single base substitution within exon 48 of the gene encoding this muscle protein.  This patient's gene mutation has most likely resulted in which of the following mRNA codon changes?

• A)CUU → AUU
• B)UAA → UAG
• C)UAC → CAC
• D)UCA → UGA
• E)UUU → UUC

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