Question

Discuss the differences in the structural features of B DNA and Z DNA.

Short answer

B-DNA is a right-handed helix with about 10 base pairs per turn, its sugar-phosphate backbone is on the outside and the major and minor grooves are well defined. Z-DNA is a left-handed helix with about 12 base pairs per turn, its sugar-phosphate backbone has a zig-zag shape, and the major groove is not well defined while the minor groove is narrow and deep.

Step-by-step solution

Understanding DNA

DNA or Deoxyribonucleic Acid is the blueprint of life. It is made up of repeating units called nucleotides. Each nucleotide contains a sugar molecule, a phosphate group, and a nitrogen base. DNA exists in different forms, two of the most common are B-DNA and Z-DNA.

B-DNA

B-DNA is the most common form of DNA in organisms. It takes up a right-handed helical conformation, with approximately 10 base pairs per turn. The sugar-phosphate backbone is on the outside, the bases are found on the inside of the helix. The major and minor grooves are well defined.

Z-DNA

Z-DNA is a high energy form of DNA, it takes up a left-handed configuration. It is found in actively transcribed DNA. The helix winds to the left in a zig-zag pattern and there are 12 base pairs per turn. In Z-DNA, the sugar-phosphate backbone has a zig-zag shape and the major groove is not well defined, while the minor groove is narrow and deep.

Comparison

Comparing both, B-DNA has a right-handed helix while Z-DNA has a left-handed helix. B-DNA has about 10 base pairs per turn, whereas Z-DNA has approximately 12 base pairs per turn. The sugar-phosphate backbone is on the outside of the helix in B-DNA, and it has a zig-zag shape in Z-DNA. Additionally, the major and minor grooves are more well defined in B-DNA as compared to Z-DNA.