In flies, the gene lightoid encodes a Rab GTPase that plays an important role in

Question

In flies, the gene lightoid encodes a Rab GTPase that plays an important role in vesicle trafficking of eye pigments. Mutants that produce nonfunctional versions of the lightoid protein have eyes with light colored patches in their eyes. Suppose that the lightoid protein functions specifically in vesicles in the cis Golgi and medial cisternae. How would each of the following processes be affected (not at all, somewhat impaired, or completely impaired) in the lightoid mutants. Give a brief answer for each.

Part A: Secretion of pigment proteins from eye cells through exocytosis

Part B: Translocation of a pigment protein into the ER.

Part C: Anterograde transport of pigment proteins from the ER to the Golgi.

Explanation / Answer

part A: rab proteins function in vesicle translocation and membrane fusion. there are various rab proteins that play a major role in vesicle trafficking along several organelles. exocytosis is also mediated by Rab proteins. therefore, secretion of pigments through exocytosis may be blocked or inefficient.

part B; translocation of pigment into ER is also mediated by some Rab proteins (eg., Rab2). hence, this translocation would also be inefficient.

part C: anterograde transport is mediated COPII coated transport vesicles from ER to golgi. Rab proteins may not have ay affect on this transport.

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