The cytoskeleton of an animal cell changes markedly betweenG1 and early M phase (prophase) of the cell cycle. Foreach of the following sentences, choose one of the options enclosedin square brackets that best describes the changes to thecytoskeleton and its components.
Before mitosis, the number of centrosomes must[increase/decrease]. At the beginning of[anaphase/prophase] in animal cells, thecentrosomes separate in a process driven partly by interactionsbetween the [plus/minus] ends of microtubulesarising from the two centrosomes. Centrosome separation initiatesthe assembly of the bipolar mitotic spindle and is associated witha sudden [increase/decrease] in the dynamicinstability of microtubules. In comparison with an interphasemicrotubule array, a mitotic aster contains a[smaller/larger] number of[longer/shorter]microtubules. Extracts fromM-phase cells exhibit[increased/decreased/unchanged]rates ofmicrotubule polymerization and increased frequencies of microtubule[shrinkage/growth]. The changes in microtubuledynamics are largely due to [enhanced/reduced]activity of microtubule-associated proteins and[increased/decreased] activity of catastrophins.The new balance between polymerization and depolymerization ofmicrotubules is necessary for the mitotic spindle to move the[replicated chromosomes/daughter chromosomes] tothe metaphase plate.
The cytoskeleton of an animal cell changes markedly betweenG1 and early M phase (prophase) of the cell cycle. Foreach of the following sentences, choose one of the options enclosedin square brackets that best describes the changes to thecytoskeleton and its components.
Before mitosis, the number of centrosomes must[increase/decrease]. At the beginning of[anaphase/prophase] in animal cells, thecentrosomes separate in a process driven partly by interactionsbetween the [plus/minus] ends of microtubulesarising from the two centrosomes. Centrosome separation initiatesthe assembly of the bipolar mitotic spindle and is associated witha sudden [increase/decrease] in the dynamicinstability of microtubules. In comparison with an interphasemicrotubule array, a mitotic aster contains a[smaller/larger] number of[longer/shorter]microtubules. Extracts fromM-phase cells exhibit[increased/decreased/unchanged]rates ofmicrotubule polymerization and increased frequencies of microtubule[shrinkage/growth]. The changes in microtubuledynamics are largely due to [enhanced/reduced]activity of microtubule-associated proteins and[increased/decreased] activity of catastrophins.The new balance between polymerization and depolymerization ofmicrotubules is necessary for the mitotic spindle to move the[replicated chromosomes/daughter chromosomes] tothe metaphase plate.
