Problem:

Question 1: You artificially raise the calcium concentration within the sarcoplasm of the muscle fiber and observe that the cell contracts normally. From this observation you conclude that the defect in muscular dysgeny occurs at which step in control of the muscle fiber?

A. Exposure of the active site on thin (actin) filaments
B. Binding of calcium to troponin
C. Release of calcium ions from the sarcoplasmic reticulum into the sarcoplasm
D. Repeated cycles of crossbridge binding, pivoting, and detachment

Question 2: Where in the muscle fiber do you suspect that the normal protein made by the mdg gene functions in normal mice?

A. motor end plate
B. triad
C. myofibrils
D. thin filaments

Question 3: All of the following conditions would have same effect on muscles (flaccid paralysis) as muscular dysgeny with a single exception. What is the EXCEPTION?

A. botulism
B. poisoning with atropine
C. poisoning with military nerve gas
D. myasthenia gravis

Question 4: You would expect the muscles from an animal afflicted with muscular dysgenesis to exhibit:

A. hypertrophy
B. atrophy

Question 5: You would expect that a dysgenic mouse dies shortly after birth because:

A. the heart fails to beat
B. vasoconstriction of the carotid artery prevents blood flow to the brain
C. vasodilation of the systemic blood vessels causes the blood pressure to drop to lethal levels
D. the respiratory muscles are unable to contract

Give reasoning with your answer.