Muscular dystropy

1. Becker Muscular Dystrophy (BMD) is a muscular dystrophy that involves a mutation in Dystrophin.

2. How do the length of the H and I bands of the sarcomere change in muscle contraction?
Both decrease

3. Pseudohypertrophy is a feature of Duchenne Muscular Dystrophy that typically presents at the calf muscles due to fibrofatty replacement of muscle.

4. What gene undergoes a frameshift mutation in Duchenne Muscular Dystrophy?
Dystrophin; mutation truncates the proteins; results in accelerated muscle breakdown. Hence, the loss of dystrophin in Duchenne Muscular Dystrophy results in myonecrosis

5. Type 1 muscle fibers are a type of muscle fiber that perform sustained contraction due to an increased concentration of mitochondria and myoglobin (i.e. increased oxidative phosphorylation capacity).
Hence these fibers are “red” fibers.

6. Which gene is mutated in Becker Muscular Dystrophy?
DMD = frameshift mutation in Dystrophin causing deletion of the protein
BMD = point mutation in Dystrophin, hence less severe
Both BMD and DMD = X-linked recessive

7. What type of mutation is seen in Duchenne Muscular Dystrophy?
Frameshift mutation – Causes a truncated Dystrophin protein and accelerated muscle breakdown

8. Where in the body does muscle weakness first appear in Duchenne Muscular Dystrophy?
Pelvic Girdle

9. How do Aldolase levels change in Duchenne Muscular Dystrophy?
Increase

10. What is the genetic inheritance of Duchenne’s Muscular Dystrophy (DMD)?
XLR

11. The Gower maneuver is a feature of Duchenne Muscular Dystrophy that involves patients using their upper extremities to help them stand up. These patients are typically young (< 5 y/o) and male (X-linked recessive).

12. How do CK-MM (Creatine Kinase) levels change in Duchenne Muscular Dystrophy?
Increase

13. What cardiac complications are seen in Myotonic Muscular Dystrophy Type 1?
Arrythmia

14. Which human gene has the longest coding region?
Dystrophin (DMD) – For this reason there is an increased risk of spontaneous mutation

15. Which type of muscle fibers are referred to as slow twitch fibers?
Type 1

16. Which type of muscle fibers typically yield hypertrophy as a result of weight training?
Type 2, fast-twitch, white muscle fibers

17. What is the typical lifespan of someone with Becker Muscular Dystrophy?
Normal

18. What is the genetic inheritance of Becker Muscular Dystrophy?
XLR

19. What type of mutation is seen in Becker Muscular Dystrophy?
point mutation

20. Troponin C is a protein in muscle that binds to Ca2+ and causes a conformational change that moves tropomyosin out of the myosin-binding site on actin filaments.

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