Question

The DNA double helix is stabilized primarily by:

• A. Covalent bonds
• B. Hydrogen bonds
• C. Ionic bonds
• D. Van der Waals forces

Hint:

Hydrogen bonds provide stability to DNA while still allowing strand separation during replication and transcription.

Answer 1

The Correct Option is B

Step 1: Understanding the structure of DNA.
DNA is composed of two antiparallel polynucleotide strands forming a double helix structure. Each strand has a sugar-phosphate backbone and nitrogenous bases projecting inward.
Step 2: Identifying the forces holding the two strands together.
The two DNA strands are held together by hydrogen bonds formed between complementary nitrogenous bases — adenine pairs with thymine via two hydrogen bonds, and guanine pairs with cytosine via three hydrogen bonds.
Step 3: Analysis of the given options.
(A) Covalent bonds: These bonds hold nucleotides together within a single strand, not between the two strands.
(B) Hydrogen bonds: Correct — hydrogen bonds between complementary bases stabilize the DNA double helix.
(C) Ionic bonds: These do not play a major role in stabilizing DNA structure.
(D) Van der Waals forces: They contribute slightly but are not the primary stabilizing force.
Step 4: Conclusion.
The DNA double helix is primarily stabilized by hydrogen bonds between complementary base pairs.