acridine orange and M phase detection

JOHN F. BOYLAN boylanjf at
Thu Mar 21 11:46:27 EST 1996

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I have a question about the mechansim by which acridine orange 
can discriminate between the G2 and M phases of the cell cycle.  
As described by Dr. Darzynkiewicz, we have been able to use 
acridine orange to separate G2 from M.  As I understand the 
procedure acridine orange fluoresces red when bound to denatured 
DNA and green when bound to double stranded DNA.  Under mild 
denaturization conditions, G2 DNA exist in the double stranded 
state.  M phase DNA exists in a more denatured state because it 
is condensed.


Why is condensed DNA more sensitive to mild denaturation?

What determines whether acridine orange fluoresces red or green 
once bound to the different types of DNA?  Does AO take on a 
different configuration once bound emitting at different 


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