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DNA Types A, B & Z


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#1 neo007

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Posted 15 April 2006 - 10:04 PM

Can anyone tell me where the A-form and Z-form of DNA is found? I understand that the B form is found in normal human cells, but where do the other two come from and do/can they exist in human cells?
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#2 chadn

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Posted 15 April 2006 - 10:13 PM

The A-form of DNA exists under conditions of dehydration or high-salt concentrations.

The Z-form I believe exists only in the lab. In addition to these three there are also C, D, E, and P forms. All of these....if I am correct are found under laboratory conditions, only. I could be wrong about this, however.
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#3 neo007

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Posted 15 April 2006 - 10:16 PM

so, the B form could potentially "denature" into the A form under high salt concentrations or with dehydration?
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#4 chadn

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Posted 15 April 2006 - 10:36 PM

B-DNA doesnt need to denature to form A-DNA.
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#5 Yggdrasil

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Posted 16 April 2006 - 03:36 AM

The A form of DNA is biologically relevant because it is the conformation taken by double stranded RNAs and DNA-RNA hybrids. Furthermore, some bacteria can convert their DNA from B-DNA to A-DNA when they form spores (Mohr, SC. et al. (1991) PNAS 88, 77-81). Supposedly, the DNA is more resistant to degradation in the A conformation than in the B conformation.

Z-DNA is primarily though to be an artifact of the laboratory and there is no evidence that it is biologically relevant.
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#6 neo007

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Posted 16 April 2006 - 09:29 PM

Are there any sites with info about A and Z form DNA in detail? I've tried searching on google, but can't seem to find anything
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#7 Yggdrasil

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Posted 16 April 2006 - 10:10 PM

Wikipedia has some basic information on A and Z DNA (http://en.wikipedia....ices_formation), while you can find the crystal structures of A & Z DNA on the PDB (http://www.rcsb.org/...th/pdb23_3.html)
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#8 neo007

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Posted 16 April 2006 - 10:51 PM

i've come across the wikipedia one before, and yeah is rather basic, but the second link seems more useful and more to what i'm looking for
thanks!
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