1. Examine the figure below showing a plaque assay. Cells were stained with a cr
ID: 192716 • Letter: 1
Question
1. Examine the figure below showing a plaque assay. Cells were stained with a crystal violet solution to visualize the results. 102 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. 12 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
a) 10-2 well indicates 100 times dilution of the stock sample (original virus sample).
10-3 well indicates 1000 times dilution of the stock sample (original virus sample).
10-4 well indicates 10000 times dilution of the stock sample (original virus sample).
10-5 well indicates 100000 times dilution of the stock sample (original virus sample).
10-6 well indicates 1000000 times dilution of the stock sample (original virus sample).
10- well indicates 10000000 times dilution of the stock sample (original virus sample).
b) It is assumed that each plaque formed is the representative of one infective virus particle. A viral plaque is formed when a virus infects a cell within the fixed cell monolayer. The virus infected cell will be lysed, and it spreads the infection to adjacent cells. The infection-to-lysis cycle will be repeated, and the infected cell area will create a plaque. A plaque is the area of infection surrounded by uninfected cells.
C) There is no cells in first three wells because all cells are lysed by the virus particles.
d) A total of 50 plaques are present in the 10-7 well.
So, the the concentration in original sample is 50 X 107 = 5 X 108 PFU/ml
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.