Genetically engineering the virus to contain sequences that can be bound by fluorescent proteins may interfere with the structure and behavior of the viral DNA, says Urs Greber, a virologist at the University of Zurich. And with the other popular technique, fluorescence in situ hybridization (FISH), “one is never sure if every [viral] DNA in the cell is equally accessible” for labeling, he says, adding that the harsh denaturing and permeabilizing conditions required for FISH may also destroy or remove viral DNA.
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Visualizing Viruses
Source: The Scientist Magazine