Zoology - Molecular Basis of Inheritance Question with Solution | TestHub

B-DNA is a helical structure with a diameter of $20\mathring{A}$ and the distance between the two base pairs is $3.4\mathring{A}$. There are 10 base pairs in each turn; hence, one turn of the helix (pitch of each helix) is approximately $34\mathring{A}$ or $3.4\mathrm{nm}(10=1.0\mathrm{nm})$. Related Theory There are three different DNA types: (i) A-DNA: It is a right-handed double helix similar to the B-DNA form. Dehydrated DNA takes an A form that protects the DNA during extreme condition such as desiccation. (ii) B-DNA: The most common DNA conformation which is a right-handed helix, normal physiological conditions. (iii) Z-DNA: Z-DNA is a left-handed DNA where the double helix winds to the left in a zig-zag pattern and play some role in gene regulation.