1. Exposure to organophosphorus pesticides (OP) is a cause of serious nerve damage. It disrupts synaptic transmission by inhibiting the enzyme acetylcholinesterase, causing death due to cardiovascular and respiratory failure.

Recombinant human acetylcholinesterase (rAChE) was obtained by genetic engineering and produced in Nicotiana benthamiana plants. It was tested as a new therapeutic treatment in mice that were exposed to OP. The following graph shows the severity of the symptoms shown by each mouse at different ratios of rAChE to OP.

(a) State the minimum ratio at which some mice showed no symptoms.

(b) Analyse the effect of increasing the ratio of rAChE to OP on the symptoms in mice.

(c) Predict what would happen if a mouse received 300 mg of rAChE and 600 mg of OP.


To test the effect of OP damage on synapses, mice were treated with rAChE, OP or both. Their diaphragms were dissected 10 days after treatment. The area of the synapse between axons and the diaphragm was measured. When the synapses are damaged by OP there is a greater area. The box plot shows the effect of different treatments on the area of the synapse.

(d) Calculate the difference in median area of synapse between the control mice and mice treated with rAChE and OP, giving the units.

(e) Describe the evidence for damage to synapses by OP provided by data in the box plot.

(f) Using the data from both graphs, evaluate the hypothesis that plant-produced rAChE could be used to protect humans or other mammals from damage caused by exposure to OP.




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