The growth of the HPV was monitored as follows: 10 9 cells and 10 6 viruses in o
ID: 64721 • Letter: T
Question
The growth of the HPV was monitored as follows: 109 cells and 106 viruses in one milliliter were incubated under appropriate conditions. Following a first infectious cycle, a direct count and a plaque assay were performed. In the case of the direct count, the mixture was diluted by a factor of 1000X after which beads were added to obtain a final concentration of 1 X 104 beads/mL. A microscopic field of vision revealed 20 beads and 150 virions. In the case of the plaque assay, 67 plaques were observed on a plate on which 0.1 mL of a 10-5 dilution was assayed.
After the last infectious cycle, a 10-8 dilution was made on the supernatant. If 0.1 mL of this dilution is applied to a monolayer of cells, how many plaques would you expect?
Explanation / Answer
PFU/ml= No of plaques / Dilution factor X volume of lysate infected with.
= 67 X 106/0.1 ml X 10 -8 = 67 X 1014 PFU/ml.
Since, the initial PFU is 67 X 106 ; From that 0.1 ml and 10-8 th dilution was taken.
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