How can mutations in different genes, functioning in different cells, lead to the same disease? From the following, choose the best responses to complete the sentences: "Physiological function requires that multiple cells work together. Various defects in different cells can impair function, leading to ___________ that are indistinguishable at the level of the whole organism. In Charcot-Marie-Tooth disease, motor nerve function can be impaired either by a problem within _______________ , or a problem in __________________ causing _______________."

Question

  Charcot-Marie-Tooth is the most commonly inherited peripheral neuropathy, and has no known cure. Patients suffer damage to motor and sensory neurons, leading to degeneration of muscles and gradual loss of motor control.

A.  defects; somatic cells; oligodendrocytes; demyelination
B.  symptoms; motor neurons; Schwann cells; demyelination
C.  symptoms; sensory neurons; Schwann cells; fast axonal transport
D.  genotypes; dendrites; axons; fast axonal transport

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content/Choose Answer
· What do you already know about components of the nervous system? What other information is related to the question?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  symptoms; motor neurons; Schwann cells; demyelination

Clarify Question
· What is the key concept addressed by the question?
        o The question is asking you to evaluate which sentence is the most logical with the context clues that are provided.
· What type of thinking is required?
        o This question is asking you to evaluate which words most accurately fit into the sentence provided.

Gather Content/Choose Answer
· What do you already know about components of the nervous system? What other information is related to the question?
        o To solve this problem, you’ll need to apply your knowledge of the difference between oligodendrocytes and Schwann cells and their functions. Oligodendrocytes are cells that myelinate axons in the central nervous system while Schwann cells serve the same purpose in the peripheral nervous system. The first blank refers to the outcome of defects that can have different causes, but that is indistinguishable at the level of the whole organism. The word that best fits here is “symptoms”. The next blank refers to a problem with motor nerve function, so “sensory neurons” does not make sense and “somatic cells” is too vague. This leaves you with answer b, which makes sense because Schwann cells lay down myelin in motor neurons. Problems with either the motor neuron itself or its myelin would result in the same symptom, a reduction in the conduction of neural signals.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o If you figured out the correct answer, good job! If not, where did you go wrong? Did you remember that oligodendrocytes are found in the central nervous system and not the peripheral nervous system as Schwann cells? Did you remember that Schwann cells are responsible for myelination of peripheral nerves and that myelination increases the conduction of action potentials? Did you understand the concept that multiple genotypes and defects can lead to the same symptoms? Did you use the process of elimination to discount answers with incorrect words?