1. Examine the figure below showing a plaque assay. Cells were stained with a cr
ID: 190227 • Letter: 1
Question
1. Examine the figure below showing a plaque assay. Cells were stained with a crystal violet solution to visualize the results 10-2 10-3 10-4 10-5 10-6 10-7 (a) What do the values indicate above each well? [2 pts.] (b) Describe in your own words what a "plaque" represents and why it forms. [2 pts.] (c) Why does it appear that no cells are present in the first three wells? [2 pts.] (d) A total of 50 plaques are present in the 10 well. What is the concentration of virus in the original sample in PFU/mL? [2 pts.]Explanation / Answer
Answer:
(a) Values indicate the dilution factor indicating the viral load
(b) The virus infects the cells and lyse them to create an empty area called plaque (an area of infection surrounded by uninfected cells)
(c) First three plates show very high viral load, as a result all the cells are lysed
(d)
Answer:
Original PFU/ml = ?
Dilution factor =10^-7 or 1/10^7
Number of plaques= 50
Volume of sample = 1 mL to the plate
pfu/ml = (no. of plaques)/( dilution factor x volume of culture plate)
pfu/ml = (50)/ (1/10^7 x 1)
pfu/ml = 50 x 10^7
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