The drug colchicine acts to

a. promote microtubule assembly.     

b. inhibit microtubule assembly.

c. sever microtubules.                        

d. block cell division.

e. cap microtubule ends.

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#Question id: 5021

#Unit 11. Evolution and Behavior

Most dinosaurs and pterosaurs become extinct at the close of the __________ era.

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#Question id: 12697

#Unit 7. System Physiology – Animal

The following test results were obtained: urine flow rate = 2.0 ml/min; urine inulin concentration = 60 mg/ml; plasma inulin concentration = 2 mg/ml; urine potassium concentration = 20 μmol/ml; plasma potassium concentration = 4.0 μmol/ml; urine osmolarity = 150 mOsm/L; and plasma osmolarity = 300 mOsm/L. What is the approximate GFR?

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#Question id: 18981

#Unit 13. Methods in Biology

The pL promoter is controlled by the cl repressor protein of bacteriophage A. In practice, a temperature-sensitive mutant of the cl repressor, cl857, is generally used to regulate pL-directed transcription. Cells carrying the temperature-sensitive cl repressor are first grown at 30°C, and 42°C

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#Question id: 1380

#Unit 4. Cell Communication and Cell Signaling

Which of the following apply to the synthesis of plant cell walls? Please select all that apply.

a) Cellulose microfibrils are formed by cellulose synthase complexes called rosettes

b) Cellulose is synthesized using cytoplasmic ATP-glucose and deposited as microfibrils directly on the outer surface of the plasma membrane.

c) Matrix polysaccharides of plant cell walls are synthesized in the Golgi apparatus and exported to the cell wall by endocytosis.

d) The direction of cellulose microfibril growth is determined by the orientation of arrays of microtubules lying just below the plasma membrane.

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#Question id: 15781

#Unit 5. Developmental Biology

Chemical regulation of stem cells takes the form of secreted proteins from surrounding cells that influence stem cell states and progenitor differentiation through endocrine, paracrine, or juxtacrine mechanisms. These signaling factors: