Difference Between B DNA and Z DNA

The key difference between B DNA and Z DNA is that the B DNA is the commonest form of DNA, which is a right-handed helix while the Z DNA is the long and thin version of B DNA, which is a left-handed helix. 

James Watson and Francis Crick in 1953 discovered the double helix structure of DNA.  Therefore, DNA appears as a twisted ladder.  Moreover, there are three major DNA helix conformations such as A DNA, B DNA and Z DNA. Among these three, B DNA is more predominate in cells, and it is the form described by Watson and Crick.

CONTENTS

1. Overview and Key Difference
2. What is B DNA
3. What is Z DNA
4. Similarities Between B DNA and Z DNA
5. Side by Side Comparison – B DNA vs Z DNA in Tabular Form
6. Summary

What is B DNA?

B DNA is the most common conformation of DNA. It is a right-handed helix, and the diameter of the helix is 2.37 nm.

Figure 01: Three Main DNA Conformations

Furthermore, it has 10 base pairs per complete turn. The distance per complete turn is 3.4 nm. The rise per base pair of B DNA is 0.34 nm, and it has a wide and deep major groove.

What is Z DNA?

Z DNA is one type of DNA conformations, which is less common. It is also known as a long and thin version of B DNA. It is a left-handed helix with the diameter of 1.84 nm.

Figure 02: Z DNA

Z DNA has 12 base pairs per complete turn. Therefore, the rise per base pair is 0.37 nm. The distance per complete turn which is the pitch is longer, and it is 4.5 nm. Major groove is flat in Z DNA.

What are the Similarities Between B DNA and Z DNA?

• B DNA and Z DNA are two conformations of DNA helix structure.
• Both are made from three components such as bases, phosphate groups and deoxyribose sugar.

What is the Difference Between B DNA and Z DNA?

B DNA and Z DNA are two DNA conformations among three types. B DNA is a right-handed helix whereas Z DNA is a left-handed helix. B DNA is the common form. It is more aligned and stacked than Z DNA. However, its diameter is less than Z DNA. The below infographic presents more details on the difference between B DNA and Z DNA.

Summary – B DNA vs Z DNA

B DNA and Z DNA are two conformations of DNA helix. B DNA is much more stacked and aligned than Z DNA. Moreover, it is the most common form, which is right-handed. On the other hand Z DNA is left-handed helix and less common than B DNA. This is the difference between B DNA and Z DNA. Furthermore, the B DNA has a wide and narrow major groove while the Z DNA has a major flat groove. Also, the helix diameter is high in Z DNA than B DNA.

Reference:

1.“Nucleic Acid Double Helix.” Wikipedia, Wikimedia Foundation, 27 July 2018. Available here
2.“Z-DNA.” Wikipedia, Wikimedia Foundation, 27 July 2018. Available here  

Image Courtesy:

1.”Dnaconformations”By Mauroesguerroto – Own work, (CC BY-SA 4.0) via Commons Wikimedia
2.”Z-DNA orbit animated small”By Richard Wheeler (Zephyris) – Own work (CC BY-SA 3.0) via Commons Wikimedia

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