The cytoskeleton of an animal cell changes markedly between G1 and early M phase (prophase) of the cell cycle
For each of the following sentences, choose one of the options enclosed in square brackets that best describes the changes to the cytoskeleton and its components.
Before mitosis, the number of centrosomes must [increase/decrease]. At the beginning of [anaphase/prophase] in animal cells, the centrosomes separate in a process driven partly by interactions between the [plus/minus] ends of microtubules arising from the two centrosomes. Centrosome separation initiates the assembly of the bipolar mitotic spindle and is associated with a sudden [increase/decrease] in the dynamic instability of microtubules. In comparison with an interphase microtubule array, a mitotic aster contains a [smaller/larger] number of [longer/shorter] microtubules. Extracts from M-phase cells exhibit [increased/decreased/unchanged] rates of microtubule polymerization and increased frequencies of microtubule [shrinkage/growth]. The changes in microtubule dynamics are largely due to [enhanced/reduced] activity of microtubule-associated proteins and [increased/decreased] activity of catastrophins. The new balance between polymerization and depolymerization of microtubules is necessary for the mitotic spindle to move the [replicated chromosomes/daughter chromosomes] to the metaphase plate.
Before mitosis, the number of centrosomes must increase. At the beginning of prophase in animal cells, the centrosomes separate in a process driven partly by interactions between the plus ends of microtubules arising from the two centrosomes. Centrosome separation initiates the assembly of the bipolar mitotic spindle and is associated with a sudden increase in the dynamic instability of microtubules. In comparison with an interphase microtubule array, a mitotic aster contains a larger number of shorter microtubules. Extracts from M-phase cells exhibit unchanged rates of microtubule polymerization and increased frequencies of microtubule shrinkage. The changes in microtubule dynamics are largely due to reduced activity of microtubule-associated proteins and increased activity of catastrophins. The new balance between polymerization and depolymerization of microtubules is necessary for the mitotic spindle to move the replicated chromosomes to the metaphase plate.
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