A 4yearold boy is referred to a genetics clinic because he has calf hypertrophy and trouble rising from the floor when seated. His creatine kinase level is 10,000 U/L. Which of the following is the BEST initial method to determine his diagnosis?

A. dystrophin immunohistochemistry on muscle tissue
B. dystrophin deletion/duplication analysis followed by sequencing
C. Western blot analysis for dystrophin on muscle tissue
D. FISH analysis for deletion/duplication detection