What would you expect to see at the end of cell division if the dividing cell was treated with oryzalin, a reagent that depolymerizes microtubules, immediately before telophase?
The correct answer and explanation is:
Correct Answer: You would expect to see a cell with replicated nuclei but no complete separation into two daughter cells.
Explanation:
Oryzalin is a herbicide that binds to tubulin, the building block of microtubules, and prevents their polymerization. Microtubules are essential components of the cytoskeleton that play a crucial role in many stages of cell division, particularly during mitosis. If oryzalin is applied just before telophase, it disrupts microtubule function at a critical point in cell division.
During telophase, the chromatids that have been pulled to opposite poles of the cell start to decondense, and the nuclear envelopes begin to reform around each set of chromosomes. Microtubules, especially those forming the mitotic spindle, help to maintain the proper positioning of chromosomes and facilitate the final steps of mitosis. Moreover, the microtubules from the central spindle contribute to forming the structure known as the phragmoplast in plant cells or help guide the cleavage furrow in animal cells, both of which are essential for cytokinesis.
If microtubules are depolymerized just before telophase, the spindle structure collapses. This causes improper chromosome positioning and interferes with the organization of the machinery needed for cytokinesis. In plant cells, the absence of microtubules prevents the formation of the phragmoplast, which guides the cell plate needed for dividing the cytoplasm. In animal cells, the contractile ring might not form correctly or be misdirected, leading to incomplete cytokinesis.
As a result, the final outcome would be a single cell containing two distinct nuclei (a binucleated cell), because nuclear division occurs, but the cytoplasm fails to divide. The lack of functional microtubules prevents successful completion of cytokinesis, leading to defective or aborted cell division.