The growth of the HPV was monitored as follows: 109 cells and 106 viruses in one
ID: 64976 • 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 1 000X 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.
1. According to the direct count, what was the number of virus/mL after the first infectious cycle?
Explanation / Answer
Number of virions = 150
In the case of the direct count, the mixture was diluted by a factor of 1 000X 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.
According to the direct count, the number of virus/mL after the first infectious cycle = 1 x 104 x 10-3 x 20 x 150
= 10 x 20 x 150 = 30000 viruses.
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