Using Fig. 6.1, name A and B.
Using Fig. 6.1, name the process taking place at C.
Using Fig. 6.1, state the effect of B entering the post-synaptic neurone.
Explain the role of acetylcholinesterase in the synapse.
Some synapses in the brain use the neurotransmitter dopamine. Once the postsynaptic membrane has depolarised, dopamine detaches from the receptor proteins and returns to the presynaptic neurone via specific transporter proteins. Schizophrenia is a condition in which certain areas of the brain have a higher than usual concentration of dopamine. The drug phenothiazine has a similar shape to dopamine and is used to treat schizophrenia. Suggest and explain what occurs at the synapse when phenothiazine is used in the treatment of schizophrenia.
DRD4 is a dopamine receptor in humans. The gene that codes for the DRD4 receptor has many alleles, although an individual can carry only two. Three alleles of the DRD4 receptor gene have these mutations: a single base substitution; a 21 base-pair deletion; a 13 base-pair deletion. The 13 base-pair deletion has the most serious effects on the structure of the DRD4 receptor protein. Suggest why this is so.
One allele of the DRD4 gene has been found more frequently amongst individuals whose personality is described as ‘impulsive and exploratory’. Describe the mechanism whereby an allele such as this could have become common in the human population.