One-way synaptic transmission occurs because
a. only dendrites can respond to electrical signals
b. more receptors for neurotransmitters are found on the presynaptic membrane
c. receptors for neurotransmitters are mostly found on the postsynaptic membrane
d. the postsynaptic cell contains most of the synaptic vesicles.

Receptors for neurotransmitters are mostly found on the postsynaptic membrane

Explanation:

One-way synaptic transmission is usually a chemical synapsis, where an electrical impulse is transmitted along the neuron's axon until it reaches the axon terminals, then a depolarization of the presynaptic membrane occurs, leading to the liberation of neurotransmitter molecules from the synaptic vesicles (located in the presynaptic membrane) into the synaptic cleft. Then the neurotransmitter molecules are captured by specific receptors found in the membrane of the postsynaptic neuron, what then leads to a hyperpolarization of the membrane followed by the generation of the postsynaptic potential.

This process can only occur in one direction because  the synaptic vesicles are only found in the axon terminals, while the neurotransmitters receptors are only found on dendrites.

identify the dna change shown in the diagram and explain how that change can result in the increased genetic diversity often seen among siblings.