What type of bond holds the two strands of DNA together?

• A. Ionic bonds
• B. Covalent bonds
• C. Hydrogen bonds
• D. Peptide bonds

Answer: (C)

The correct answer is hydrogen bonds, which play a crucial role in stabilizing the structure of DNA. In DNA, the two strands run antiparallel to each other and are wound around one another to form a double helix. The strands are connected by complementary base pairing, where specific bases on one strand pair with bases on the other strand (adenine with thymine and cytosine with guanine).

These base pairs are held together by hydrogen bonds, which, while relatively weak compared to other types of bonds, are significant in large numbers. This weak nature of hydrogen bonds allows the DNA double helix to be flexible and enables the strands to separate easily during processes such as DNA replication and transcription.

Other types of bonds mentioned, such as ionic bonds, covalent bonds, and peptide bonds, do not play a role in holding the two strands of DNA together. Ionic bonds involve the attraction between positively and negatively charged ions and are not relevant in the context of the DNA structure. Covalent bonds are present within each DNA strand, linking the sugar and phosphate backbone, but they do not connect the two strands to each other. Peptide bonds are specific to proteins, linking amino acids together, and are unrelated to the structure of DNA.