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

97. An analysis of the spatial orientation of the B-DNA double helix shows that the glycosidic bonds linking the bases to the sugar rings project at unequal angles. This structural asymmetry means that the phosphodiester backbones are

A. Arranged directly opposite each other, forming a perfectly symmetrical cylinder
B. Arranged closer together on one side of the helix than the other, creating distinct grooves
✓
C. Linked covalently across the core via disulfide bridges
D. Restricted to a rigid left-handed zigzag spatial orientation

📝 Explanation

Because the glycosidic bonds project unevenly, the backbones wind asymmetrically around the axis, creating alternating major and minor grooves.

📖 Additional Information

  • Arranged directly opposite each other, forming a perfectly symmetrical cylinder
  • Arranged closer together on one side of the helix than the other, creating distinct grooves
  • Linked covalently across the core via disulfide bridges
  • Restricted to a rigid left-handed zigzag spatial orientation

Because the glycosidic bonds project unevenly, the backbones wind asymmetrically around the axis, creating alternating major and minor grooves.

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