The symptoms of a certain inherited disorder in humans include breathing problems and, in males, sterility.  Which of the following is a reasonable

hypothesis for the molecular basis of this disorder?  a.  a defective enzyme in the mitochondria, b. defective actin molecules in cellular microfilaments, c. defective dynein molecules in cilia and flagella, d. abnormal hydrolytic enzymes in the lysosomes, or e.  defective ribosome assembly in the nucleolus?

Expert Answers

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Assuming that the two symptoms you have listed are the only abnormalities, this scenario points to answer c, defective dynein molecules in the cilia and flagella. Axonemal dynein is a protein that functions in creating motion in flagella and cilia by causing sliding of the microtubules within the organelles. (There are two kinds of dynein, axonemal, which is found only in cells that have cilia or flagella, and cytoplasmic dynein, which occurs in all cells and helps to transport molecules along the cytoskeleton.)

The respiratory difficulty in this scenario can be traced to defective cilia within the respiratory tract, which could lead to a buildup of mucus and fluids which would interfere with respiration. Sperm are the only human cells that have flagella, and flagella which are unable to swim would certainly lead to male infertility.

The other four choices in the question you have presented would all affect a much wider variety of bodily functions, as they are all things which are common to most, if not all, cells.

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