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

46. The chemical feature that prevents the standard DNA double helix from adopting an A-form configuration under normal physiological conditions is the

A. Absence of a 2' hydroxyl group on the deoxyribose sugar
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B. High concentration of guanine-cytosine pairs
C. Negative charge of the phosphate groups
D. Abundance of water molecules in the surrounding cytosol

📝 Explanation

Lacking a 2'-OH group allows deoxyribose to prefer a C2'-endo sugar pucker, which drives the flexible, uncrowded B-DNA geometry.

📖 Additional Information

  • Absence of a 2' hydroxyl group on the deoxyribose sugar
  • High concentration of guanine-cytosine pairs
  • Negative charge of the phosphate groups
  • Abundance of water molecules in the surrounding cytosol

Lacking a 2'-OH group allows deoxyribose to prefer a C2'-endo sugar pucker, which drives the flexible, uncrowded B-DNA geometry.

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