# DBT JRF 2020 — Question 31

Exam: DBT JRF 2020 · Section: A · Topic: Biochemistry · Difficulty: Easy

## Question

Nucleic acid structures are stabilized by

## Options

- **A.** covalent interactions
- **B.** hydrophobic interactions and hydrogen bonding
- **C.** covalent and hydrophilic interactions
- **D.** hydrophilic interactions

## Answer

Option B

## Explanation

The DNA double helix is stabilised by two types of non-covalent forces: (1) Base stacking (hydrophobic interactions) — the planar aromatic rings of adjacent bases stack on top of each other, minimising contact with water (hydrophobic effect). This contributes ~60–70% of helix stability. (2) Watson-Crick hydrogen bonds — A:T pairs share 2 H-bonds; G:C pairs share 3 H-bonds. These bonds contribute specificity and additional stability. Covalent bonds (phosphodiester backbone) exist within each strand but do not stabilise the double helix between strands. Hydrophilic interactions do not stabilise the helix.

Source: https://mypyqbuddy.com/questions/nucleic-acid-structures-are-stabilized-by-6a05a8a02adafec470293205