1- GTP-gamma-S is a chemically modified version (analog) of GTP that behaves lik

Question

1- GTP-gamma-S is a chemically modified version (analog) of GTP that behaves like GTP in every way, except that it cannot be hydrolyzed into GDP. For this question, name which cytoskeletal element will behave differently in the presence of GTP-gamma-S. Additionally, describe how filament length, number, and stability/dynamics will change if assembled using GTP-gamma-S.

2- Choose a cellular structure formed by this cytoskeletal element. Describe that structure’s normal function in the cell and how applying GTP-gamma-S to a cell might alter that structure’s normal function.

Explanation / Answer

1) Microtubules composed of alpha and beta-tubulins are required for the formation of the microtubules during various cellular processes.

Beta-tubulin binds to the GTP which is required for the polymerization of microtubules at the plus end of growing mitotic spindle. Hydrolysis of GTP to GDP by beta-tubulin is required for depolymerization of microtubules.

Binding of GTP-gamma-S to beta-tubulin affects the depolymerization of microtubule filaments.

When beta-tubulin is bound with GTP-gamma-S the filament length increases beyond 50 micrometers, their numbers increase in cells drastically and the microtubule filaments are highly stable without any depolymerization.

2) The mitotic spindle is composed of microtubules formed from alpha and beta-tubulins. During cell division polymerization and depolymerization of the mitotic spindle is required for chromosome segregation.

Binding of beta-tubulin to GTP-gamma-S affects the depolymerization of the mitotic spindle. This affects the chromosome segregation of chromosomes resulting in cells with polyploidy

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