Question

1. Why is DNA stable in an aqueous solution, at pH 7.0, and room temperature?

Answer 1

Here DNA is made up of nucleotides(one base+phosphate+sugar)and  described as double helical model in which nitrogen bases are arranged in such a way that it provides hydrophobic effects by burying bases interior of double helix increases its stability , they held together by hydrogen bonding and charge -charge interactions provide stability to extreme conditions.

Nitrogen bases undergoes keto-enol tautomezism here keto form (C=O) is called as lactam enol from is known as lactim(-OH) .At pH VALUE 7 keto from(more stable) is in highest amount that stabilizes the molecule and at the same time phosphate groups in DNA molecules are in negative charge at this pH charge -charge repulsion places this groups opposite direction stabilizes the molecule and room temperature it exists as highly viscous as the temperature increases it viscosity decrease that ultimately effects its physical and chemical properties