Question

Which of the following statements about the structure of double-stranded DNA is FALSE? 1. DNA is stabilized primarily by H-bonding between the bases. 2. Only non-covalent forces stabilize the helix so that the DNA can unwind during replication and transcription. 3. The phosphodiester backbone interacts with Mg2+ in the cell. 4. Some groups of the bases are exposed in the grooves of double-stranded DNA.

Answer 1

1. DNA is stabilized primarily by H-bonding between the bases.

Hydrogen bonding is not only the responsible for DNA stabilisation, instead base stacking and solvent interactions are major important factors imparting stability to double helix. Base stacking accounts for approximately more than 50 percent of total free energy stabilizing DNA. Van der Waals interactions, electrostatic interactions, and solvent effects define the geometry and associated energies of stacked bases.