Z - DNA: comparison with A-DNA and B-DNA

The most common form of DNA that occurs in living organisms is B-form or Watson and Crick's model of DNA. Under certain conditions, this form changes its configuration.

There are 6 different morphological forms of DNA: A, B, C, D, E and Z. Three biologically active forms of DNA are A-DNA, B-DNA, and Z-DNA.

A-DNA: this form is double-stranded, right-handed helical DNA. It is a dehydrated form that occurs in an environment richer in Na+ and less water. It shows 11 base pairs per turn of the helix and a diameter of 23 A. The height of the pitch is 28 A and axial rise is 2.56 A. The sugar-phosphate backbone is regular. The repeating units are mononucleotides. It shows the presence of 2 deep groves and 2 shallow groves.
B-DNA: occurs at low salt concentration and a high degree of hydration (i.e. normal conditions).
Z-DNA: Rich et al. working at MIT, USA studied the molecular structure of DNA fragments at atomic resolution. They proposed a Z-form of DNA along with B-DNA.
The Z-DNA shows the following characteristics:

 It is stabilized by high salt concentration.
 It is left-handed DNA.
 It is a double-helical structure with a zig-zag sugar-phosphate backbone.
 In Z-DNA, the repeating unit is a dinucleotide and the sugar residues have an alternating orientation of dinucleotide.
 In Z-DNA, 12 base pairs are present per turn.
 The height of the pitch is 45 A.
 The diameter of the helix is 18 A

For additional information about DNA and Nucleic acids, you can also refer to

[swapnilombale]

U are amazing sir!!🙏🏻 this is so confusing topic...and u made it very easy for the students!🙏🏻 thanks a ton, sir!🙌

[udaykhopade]

Real clg mde offline lectures hotE tva kadi pat jhale nahi. BUT Online you tube lectures attended karunch pat jhale.. SIR EK NUMBER GREAT SIR

[sampadabachche]

Such briliant lecture sir DNA helical structure.I am lucky sir because I am your student sir

[krishanuchoudhury]

Thank you so much read watson mol bio but was missing some concepts so can visualize with the model! Thank you very much🎉❤

[ankitjangir]

Such a nice explanation.. 👌
Where is various RNA forms, DNA replication and gene regulation...??? Plzz make videos on these topics, sir...

[drinnocent_bot]

Nice Idea of helical structure Sir...
It is my badluck sir that I am not your student. 😍🙏

[Bio_Microbio_LifSci_Tut_Mentor]

Please tell in which form of DNA syn- & anti- conformation around the glycosidic bond are present?

[anilganta]

Sir please do more videos on topics like Carbohydrates, Amino acids, peptides, Proteins, Enzymes, Lipids and Nucleic acids for BSc level... please