Most of the biologically active DNA exists in the Watson -Crick helical form. This is the B-form of DNA. The double helix is able to assume other forms, depending upon varying environmental conditions.
Forms of DNA
- 6 different morphological forms of DNA : A,B,C,D,E & Z
- A,B,C & D are right handed helices
- B & Z occur in rigidly controlled experimental conditions
- A-DNA is the dehydrated form which occurs in an environment richer in Na+ & less of water
- B-DNA occurs under salt concentration & high degree of hydration
- C-DNA & E-DNA are seen under special environmental condition &have slightly different conformation so do not occur in vivo
- Z-DNA is left handed helices. Z-DNA, is the skinniest DNA, with only one groove and is stabilized by high salt concentration.
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| B-DNA, A-DNA and Z-DNA |
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| Comparison Chart- B-DNA, A-DNA, and Z-DNA |