Parkinson's disease is caused by the death of neurones that release the transmitter dopamine. Scientists made iPS cells from patients and caused them to differentiate into dopamine-releasing neurones. These were transplanted into monkeys that had symptoms similar to Parkinson's disease. The mean movement score was then measured. The error bars show ± one standard deviation.
Name the type of cell that the iPS cells were made from.
[1]
Using the chart, describe the evidence that the iPS-derived neurones improved movement.
[2]
Suggest why the scientists tested the treatment in monkeys before using it in humans.
[2]