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BIO NMDCAT Structure of DNA
nmdcat.online July 3, 2026

87. A synthetic oligonucleotide is designed with a high concentration of methylated cytosine bases (5-methylcytosine) in a region of repeating CG steps. Under high salt laboratory conditions, this specific DNA fragment undergoes a structural transition from a right-handed B-form helix into a left-handed conformation characterized by a zigzag backbone geometry. This alternative structure is

A. A-DNA
B. Z-DNA
✓
C. C-DNA
D. H-DNA

📝 Explanation

Z-DNA is a left-handed helical variant with a zigzag sugar-phosphate backbone, favored by repeating purine-pyrimidine steps, high salt, or methylation.

📖 Additional Information

  • A-DNA
  • Z-DNA
  • C-DNA
  • H-DNA

Z-DNA is a left-handed helical variant with a zigzag sugar-phosphate backbone, favored by repeating purine-pyrimidine steps, high salt, or methylation.

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