Final answer:
The bond that holds neighboring subunits in a single strand of DNA is the phosphodiester bond. It is part of the sugar-phosphate backbone and is stronger than the hydrogen bonds which connect two DNA strands together.
Step-by-step explanation:
The type of bond that holds together neighboring subunits in a single strand of DNA is the phosphodiester bond. This bond forms between the phosphate group of one nucleotide and the 3' hydroxyl group of another nucleotide's sugar, resulting in a sugar-phosphate backbone that is essential for the structure of DNA. While hydrogen bonds do play a key role in the structure of DNA, they are the forces that connect two strands of DNA together, rather than connecting nucleotides within a single strand.
Phosphodiester bonds allow for the long chains of nucleotides to form the characteristic double-helix structure, where the two strands are held parallel by hydrogen bonds between complementary bases. It's important to note that the phosphodiester bond is a covalent bond, which is relatively strong compared to hydrogen bonds and is vital in maintaining the integrity of the DNA molecule.