Q29 - Muscle Fiber-Type Gene Expression Across Three Human Leg Muscles

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

The skeletal muscle fibers are divided into three types depending on the speed and energy sources of muscle contraction: Type I: Slow twitch, oxidative muscle fibers. Type IIa: Fast twitch, oxidative muscle fibers. Type IIb: Fast twitch, glycolytic muscle fibers. Figure Q.29 shows the correlation of mRNA expression levels of the genes Myh7, Myh2, and Myh1, specific for muscle fiber types I, IIa, and IIb respectively, in the human quadriceps, gastrocnemius, and soleus muscles.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. The soleus muscles of the sprinter athletes are prone to be more developed than those in the marathon athletes.

B. The ratio of mitochondria number per muscle mass in the quadriceps muscle is less than that in the gastrocnemius muscle.

C. The soleus muscle contains less sarcoplasmic reticulum than the gastrocnemius muscle does.

D. Regularly doing the endurance exercise for a long period of time can increase the number of glycolytic muscle fibers in the gastrocnemius muscles.

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Question reproduced from IBO 2016, Theoretical Paper A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)