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RNA helix: base number

daj (David Johnston) daj at nhm.ac.uk
Thu Jul 7 03:49:32 EST 1994

On 6 Jul 1994 20:07:40 GMT,
  Hanson Lab writes:

> If one considers RNA as a helical form, how
>many bases between each helical turn?  It should be different from DNA,

A part answer :

According to Strier, (Classic biochem text whose title I cannot remember!)

A-DNA = 11 bases per turn
B-DNA = 10.4 bpt
Z-DNA = 12 bpt

DS RNA and RNA-DNA hybrids adopt a form very similar to A-DNA "the 2'-OH of 
ribose prevents RNA from forming a Watson-Crick type helix because ofsteric 
hindrance. O-2' cannot fit into a B-helix because it would come too close 
to three atoms of the adjoining phosphate group and one in the next base... 
In A-DNA, by contrast, O-2' projects outwards, away from the other atoms"

See also article by R.E. Dickerson in Sci Amer 1983.

David A. Johnston
Dept of Zoology, The Natural History Museum, Cromwell Road,
South Kensington, London SW7 5DB. England
(tel 071 9389297, fax 071 9388754, email daj at nhm.ac.uk)

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