ART 9C Study Guide - Quiz Guide: Green Fluorescent Protein, Halorhodopsin, OptogeneticsExam
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Spring 2019 Name _______________________________________
Experimental Design Worksheet
Part I – Understanding Optogenetics
1. During Week 5, we will use optogenetics to study the neuronal populations that
are involved in controlling habituation. We will exam 4 different worms:
Pmec-4::ChR2 is a worm that expresses ChR2 under the Pmec-4 promoter.
This means that ChR2 is expressed in any cell that Pmec-4 is expressed. In
other words, ChR2 is targeted to the Pmec-4-expressing neuronal population.
Tph-1::ArchT::gfp is a worm that expresses ArchT under the Tph-1 promoter.
ArchT is tagged with green fluorescent protein (gfp). Like halorhodopsin, ArchT
is an optogenetic tool that silences whatever neuron in which it is expressed. In
contrast to halorhodopsin which allows Chloride anions to pass into the cell,
thereby hyperpolarzing it, ArchT is a proton pump which hyperpolarizes a cell by
pumping protons out.
Myo-3::Halo/NpHR::CFP is a worm that expresses Halo/NpHR under the Myo-3
promoter. Halo/NpHR is tagged with cyan fluorescent protein (CFP).
Halo/NpHR is the shorthand for halorhodopsin.
What kind of worm is Tph-1::ChR2::gfp?
2. The key to implementing optogenetics is where your optogenetic tool (ChR2,
Halo/NpHR, or ArchT) is genetically targeted. The promoter sequence dictates
where your optogenetic tool is expressed. Research Tph-1, since expression of
this gene dictates where your transgene is expressed in Tph-1:ChR2::gfp
worms. Explain what types of cells express Tph-1.
3. What does shining red light on Tph-1:ChR2::gfp worms do to them?
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