What is the Difference Between B DNA and Z DNA?

B-DNA and Z-DNA are two different conformations of DNA helixes. The main differences between them are:

1. Helix handedness: B-DNA is a right-handed helix, while Z-DNA is a left-handed helix.
2. Repeating unit: In B-DNA, the repeating unit is 1 base pair, while in Z-DNA, the repeating unit is 2 base pairs.
3. Helix diameter: B-DNA has a helix diameter of 20 Å, while Z-DNA has a diameter of 18 Å.
4. Major and minor grooves: B-DNA has a wide and deep major groove and a narrow and deep minor groove, while Z-DNA has a narrow and deep major groove and a wide and shallow minor groove.
5. Number of base pairs per turn: B-DNA has 10.5 base pairs per turn, while Z-DNA has 12 base pairs per turn.
6. Distance between adjacent deoxyribonucleotides: In B-DNA, the distance between adjacent deoxyribonucleotides is 0.34 nm, while in Z-DNA, it is 0.37 nm.
7. Stability: B-DNA is stable and easy to observe, while Z-DNA is unstable and difficult to observe.

B-DNA is the most common DNA conformation found under normal physiological conditions, while Z-DNA is less common and can be formed under specific conditions, such as high salt concentrations. Z-DNA is believed to play a role in gene expression regulation and genetic recombination.

Comparative Table: B DNA vs Z DNA

There are three major families of DNA helices: A-DNA, B-DNA, and Z-DNA. The helical structure of DNA is variable and depends on the sequence as well as the surrounding environment. Here is a table comparing the differences between B-DNA and Z-DNA:

B-DNA is the most common and widely studied form of DNA, featuring a right-handed double helix with 10 base pairs per turn, an axial rise of 0.34 nm per base pair, and a helix pitch of 34° per base pair. On the other hand, Z-DNA is a left-handed helix with 12 base pairs per turn, an axial rise of 0.45 nm per base pair, and a helix pitch of 45° per base pair. Z-DNA is found in certain regions of the genome, particularly in alternating purine-pyrimidine sequences (e.g., GCGCGC).