What type of bond is formed between nucleotides in a DNA strand?

• A. Hydrogen bond
• B. Ionic bond
• C. Phosphodiester bond
• D. Peptide bond

Answer: (C)

The correct answer is the phosphodiester bond, which is essential for forming the backbone of a DNA strand. This type of bond occurs between the phosphate group of one nucleotide and the hydroxyl group on the sugar of another nucleotide. Specifically, the phosphodiester bond connects the 3' carbon atom of one sugar molecule to the 5' phosphate group of the next nucleotide in the sequence, creating a long chain that forms the DNA strand.

Understanding the structure of DNA, these bonds form the sugar-phosphate backbone of the double helix. This backbone is vital as it provides stability and structure to the DNA molecule, allowing it to carry genetic information.

In contrast, other bond types mentioned are not involved in linking nucleotides in a DNA strand. Hydrogen bonds, while important in holding the two strands of DNA together at the bases, do not connect the nucleotides. Ionic bonds involve interactions between charged molecules but are not relevant in the context of linking nucleotides. Peptide bonds are specific to protein synthesis and connect amino acids rather than nucleotides. Thus, the phosphodiester bond is uniquely suited for the task of forming DNA strands.