In mice a reduction in the expression of the Sortin Nexin 27,(SNX27) gene results in synaptic dysfunction in the brain. Theexpression of human SNX27 (cytogenetic location: 1q21) is reducedin Down syndrome patients although there is no mutation in theSNX27 gene, and this reduction may be a cause of some of the mentaldefects in Down syndrome patients (Wang etal. 2013, Nature Medicine19, 473-480). One hypothesis is that this reduction in SNX27in Down syndrome patients is caused by an increase in the amount ofthe negative regulatory RNAi molecule miR-155, (cytogeneticlocation: 21q21.3). You have been asked to determine whethermiR-155 is increased in Down syndrome patients.

a. Describe what test or tests you would do, and how you woulddo them.

b. What results would you would expect if this hypothesis aboutmiR-155 is correct?

c. Briefly explain why you think your results support thehypothesis