Disassembly of the nuclear envelope ________________
(a) causes the inner nuclear membrane to separate from the outer nuclear membrane.
(b) results in the conversion of the nuclear envelope into protein-free membrane vesicles.
(c) is triggered by the phosphorylation of integrins.
(d) must occur for kinetochore microtubules to form in animal cells.
(d) In animal cells, kinetochore microtubules cannot form if the chromosomes in the nucleus are separated from the microtubules in the cytoplasm because of the presence of the nuclear envelope. (But in some other cells, such as the yeast S. cerevisiae, the nuclear envelope never breaks down and yet chromosomes can attach to microtubules emanating from the spindle poles within the nucleus.) The nuclear envelope disassembles by breaking up into vesicles containing lipids from both the outer and inner envelopes [choice (a)]. Integral membrane proteins of the nuclear envelope and some of the nuclear lamins remain associated with the vesicles [choice (b)]. Phosphorylation of lamins (not integrins) triggers the breakdown of the nuclear lamina [choice (c)].
You might also like to view...
A reducing medium is used to culture ________ organisms.
A. pathogenic B. aerobic C. anaerobic D. fastidious
Iron deficiency is often indicated by yellowing in newly formed leaves. This suggests that iron is _____
A) a relatively immobile nutrient in plants B) tied up in formed chlorophyll molecules C) concentrated in the xylem of older leaves D) concentrated in the phloem of older leaves E) found in leghemoglobin and reduces the amount available to new plant parts
When cortisol binds to the glucocorticoid receptor, HSP90 is released
Indicate whether the statement is true or false
The biome most known for its rich, deep topsoil is:
a. tundra b. taiga c. tropical rain forest d. desert e. grassland