The DNA molecule is described as the two right-handed polynucleotide chains coiled about the same axis. What is this structure called?

The DNA molecule is described as the two right-handed polynucleotide chains coiled about the same axis. What is this structure called?

• A. Single Helical Strand
• B. Double Helix
• C. Triple Helix
• D. Quadruple Helix

Answer: (B)

Two right-handed polynucleotide chains coiled about the same axis describe a double helix. In this setup, the sugar–phosphate backbones form the outer edges while the bases pair inside the helix, holding the two strands together. The two strands run in opposite directions (antiparallel) and twist clockwise as you move along the molecule, creating the familiar helical shape. This is the standard form of DNA in cells, with two strands intertwined. A single helix would mean only one strand, which doesn’t account for base pairing, while a triple or quadruple helix would require three or four strands bound together—uncommon for DNA under normal conditions. So the described structure corresponds to a double helix.

Two right-handed polynucleotide chains coiled about the same axis describe a double helix. In this setup, the sugar–phosphate backbones form the outer edges while the bases pair inside the helix, holding the two strands together. The two strands run in opposite directions (antiparallel) and twist clockwise as you move along the molecule, creating the familiar helical shape.

This is the standard form of DNA in cells, with two strands intertwined. A single helix would mean only one strand, which doesn’t account for base pairing, while a triple or quadruple helix would require three or four strands bound together—uncommon for DNA under normal conditions. So the described structure corresponds to a double helix.