1. You have constructed a cell strain whose actin is fused with a photo-activate
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Question
1. You have constructed a cell strain whose actin is fused with a photo-activated green fluorescent protein, PA-GFP. When PA-GFP is first expressed, it starts as non-fluorescent. It is activated by a brief laser pulse, after which it fluoresces similarly to regular GFP. Suppose you activate the actin-PA-GFP in a small spot close to the leading edge of a crawling cel. A. (2pts) Would you expect the fluorescent spot to move towards the leading edge, towards the trailing edge, or stay stationary with respect to the cell? Why? B. (2pts) Eventually, you observe that the fluorescent spot disappears. How can you explain this result? (You can assume that once activated, the PA-GFP will not photobleach or turn off.)Explanation / Answer
A.
I would expect that fluorescent spot to move towards leading edge. As cell starts crawling, actin monomers move toward the leading edge, polymerize and form actin filaments. These actin filaments act as a driving force for cell movement. Actin monomers are continuously polymerize and depolymerize from actin filament in ATP dependent process.
B.
May be as ATP is converted to ADP and then actin monomer depolymerizes from filament, the fluorescence disappears from the monomer.
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