How does Becker muscular dystrophy differ from Duchenne in dystrophin expression?

• A. Becker has no dystrophin
• B. Becker has some dystrophin present (truncated/partially functional); milder and later onset
• C. Becker has increased dystrophin
• D. Becker is not a dystrophinopathy

Answer: (B)

Becker muscular dystrophy differs from Duchenne in how much dystrophin is produced and how functional it is. In Duchenne, mutations typically disrupt the reading frame so no functional dystrophin is made, leading to early, severe muscle weakness. In Becker, mutations usually preserve the reading frame, producing dystrophin that is truncated or partially functional but present at reduced levels, which makes the disease milder and with a later onset. This partly functional dystrophin helps stabilize muscle membranes during contraction, reducing damage compared with Duchenne. So the best description is that Becker has some dystrophin present (truncated/partially functional) and a milder, later-onset course. Becker is still a dystrophinopathy, not a condition with increased dystrophin or no dystrophin.