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PCAT Biological Processes – Microfilament Polymerization

Cytochalasin B (CB) is a small, hydrophilic molecule that interferes with microfilament polymerization without measurably affecting microtubule function. Eukaryotic cells treated with CB in vitro are most likely to display abnormal:

A. chromosomal alignment during prophase.
B. chromosomal separation during anaphase.
C. cytokinesis.
D. mitochondrial replication during early prophase.

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C is correct. Cytokinesis involves a contractile ring complex, consisting of actin filaments (microfilaments) and myosin motor proteins. Interference with microfilament polymerization is likely to compromise contractile ring function and disrupt cytokinesis. Chromosomal alignment occurs during metaphase (making Choice A incorrect), and mitochondrial replication occurs during interphase (Choice D is wrong). Chromosomal separation involves the spindle apparatus, which is composed of microtubules, not microfilaments.

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