Re: Why is ethidium bromide such a toxic mutagen?

Dear Emily,

regarding why ethidium bromide is such a toxic mutagen, I'd like to tell 
you first that although I'm quite new at this organization, I'll try and 
help you in understanding your problem.

Attached to this response you'll find some descriptions about ethidium and 
its nature as an intercalator. Intercalators, just as described, are 
charged compounds that insert themselves between base pairs. 

I hope you have already covered DNA REPLICATION and TRANSCRIPTION AND 
TRANSLATION.For it is the crucial basis for understanding the effects of 
ethidium bromide on the cell as a whole. As you know the cell is depended 
on separating its DNA strands for replication and transcription in order 
for DNA polymerase or RNA polymerase to copy the genetic information 
respectively. 
BUT if the cell was exposed to ethidium bromide it would incorporate itself 
between the base pairs of the DNA and thus prevent such mechanisms of 
replication or further protein synthesis. In that way it would behave 
toxic, as the cell would soon die because it 1. CAN'T replicate anymore and 
2. Because no further proteins that would enable the cell to survive are 
synthesized. 

Nevertheless, due its good fluorescence characteristics and the fact that 
it binds to DNA, ethidium bromide is being used frequently in molecular 
biological and biotechnical research.  However, as you just stated because 
it is such a toxic mutagen people are trying to substitute ethidium bromide 
by other compounds that have the same fluorescence abilities and are less 
toxic. 

As I can think as your definition of a "toxic mutagen", is that as a 
mutagen it effects the basis for heredity- the DNA of a cell. And it is so 
"toxic" because it prevents the cell from accessing its genome to carry out 
its necessary protein synthesis to survive.

I hope to have answered your question sufficiently and I'd like to mention 
that I strongly encourage YOU and your peers to keep asking these kind of 
questions. They should contribute to your all's understanding of the field 
of molecular biology, I hope, and that's what we would like to achieve.
If you should have any further questions, you can also mail me directly at:

snottebaum@hotmail.com 

I'd be glad to answer every question you had for me.

Sincerely,

Sven Nottebaum


Pictures:

1. This shows you the structure of ethidium bromide and how it incorporates 
itself between base pairs of the DNA



2. This is a definition of intercalors ( just as ethidium bromide) from a 
very interesting textbook, dealing with Molecular Biology. If you should 
ever think about produding a bit further into this field, I highly 
recommend this book. It's called: "Molecular Biology" and comes from the - 
Instant Notes Series.(Instant notes in Molecular Biology; by Turner, 
McLennan, Bates and White)