If a neuron had a mutation that prevented the production of voltage gated Na + channels, what function would the neuron NOT be able to accomplish?

The answer is generation and propagation of action potential.

Na + channels are important for generation and propagation of action potential. In normal neurons, when neurons hit threshold and action potential is triggered, the Na + channels open and Na + ions enter the neuron. After the depolarization of membrane, Na + channels inactivate. Thus, w ithout Na + channels, neurons would not be able to depolarize and consequently, the action potential would not be generated.