Sinister DNA?

Dr. David Starrett dstarret at BIOLOGY.SEMO.EDU
Wed Apr 15 17:52:42 EST 1998

At 01:39 PM 4/15/98 -0700, you wrote:
> I asked a distinguished molecular biologist this question. He didn't know
>the answer either so I feel bold enough to ask you. The only diagram that I
>had at hand showed DNA as a dextral spiral. Is it always thus in actuality
>or sinistral or 50/50? Does the underlying chemistry dictate whether the
>spiral is clockwise or counter clockwise? How relevant is this to the
>additional twists which permit the two strands to separate at division
>without becoming intertwined?
This is the difference between B and Z forms of DNA.  Any DNA binding
proteins, such as enzymes, transcription factors, etc. would not fit if the
DNA were spiraled in the other direction.  DNA is also less stable in the
sinister form (Z DNA).  Z DNA is kinky and has really only one groove
instead of the major and minor grooves found in B DNA.  It lloks like a
mess compared to the smooth spiral seen in B DNA.

Dave Starrett

* Dr. David Starrett                                      *
* Biology Department, MS 6200                             *
* Southeast Missouri State University                     *
* Cape Girardeau, MO  63701                               *
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