Question

1. What will happen if you push the plunger on your micropipettor past the first stop prior to drawing fluid?

(a) You will draw air into the tip. (b) You will eject the tip. (c) You will draw excess fluid into the tip when drawing the fluid. (d) You will damage the tip. (e) You will damage the spring inside the micropipettor.

2. What is the length of the side of each of the smallest squares on your hemocytometer? (a) 1 m (b) 50 m (c) 0.1 mm (d) 0.2 mm (e) 1 mm

3. Why did you subtract the control (blank) A600 value from those of all wells that had samples? (a) because it was necessary to divide the cellular A600 value by the dilution factor (b) because 600 nm is the visible-light wavelength that is most strongly absorbed (c) because there were 6 samples, but you only used the value from one of them (d) because there was an equal volume of fluid in each of the wells (e) because there might be a background level of absorbance that has nothing to do with cells

4. You combine 250 μL of India-Ink solution with 500 μL H2O. What is the ink:water dilution factor? (a) 25% (b) 1:2 (c) 66.6% (d) 3:1 (e) 1/3

5. Why should you agitate a yeast solution before you draw from it? (a) yeast cells are able to swim and cluster at the top (b) dead cells will be excluded from the aliquot that you draw (c) it will ensure a uniform and repeatable concentration of cells (d) to induce anaerobic respiration in all cells (e) budding cells will complete cytokinesis

Please answer all questions

Answer 1

1. Micropipette has two stops, the first one for the fluid intake, and the second is to eject the fluids completely. While drawing the fluid, if presses past the first stop, more than the intended liquid is drawn in. Hence answer is option C.

2. The length of the smallest square is 50 um. Option B.

3. Blank readings are often subtracted from the sample readings to remove the background. In a sample, other liquid constituents like media, buffer, salts can also show absorbance. But they have nothing to do with the sample. Hence their absorbance must be removed using a blank which has all components except for sample. Option E is the answer.

4. 250 ul of dye is combined with 500 ul water. Total volume = 750. So the ratio of dye to water = 250/750 = 1/3. So the answer is option E.

5. Before drawing cells, culture must be agitated to get a uniform mix of cells. for better repeatability. Option C is the answer.