Using Fig. 6.1, name A and B.
Name the process taking place at C.
State the effect of B entering the post-synaptic neurone.
Using Fig. 6.1, explain the role of acetylcholinesterase in the synapse.
Some synapses in the brain use the neurotransmitter dopamine. After the postsynaptic membrane has been depolarised, dopamine detaches from the receptor proteins and returns to the presynaptic neurone through specific transporter proteins. Schizophrenia is a condition in which the dopamine concentration is higher than usual in certain regions of the brain. Phenothiazine has a similar shape to dopamine and is used to treat schizophrenia. Suggest and explain what happens at the synapse when phenothiazine is used in the treatment of schizophrenia.
DRD4 is a dopamine receptor found in humans. The gene that codes for the DRD4 receptor has many alleles, but any one individual can possess only two. Three alleles of the DRD4 receptor gene show the following mutations: • a single base substitution • a 21 base-pair deletion • a 13 base-pair deletion. The 13 base-pair deletion has the most severe effect on the structure of the DRD4 receptor protein. Suggest why this is so.
One allele of the DRD4 gene has been found more often among individuals whose personality is described as ‘impulsive and exploratory’. Describe the mechanism by which an allele like this could have become common in the human population.