What type of bond connects nucleotides along each strand?

The bond that connects nucleotides along each DNA strand is a phosphodiester bond.

Each nucleotide contributes a deoxyribose sugar, a phosphate group, and one of the bases adenine, thymine, cytosine, or guanine. In the backbone, a phosphate links the 3′ carbon of one deoxyribose to the 5′ carbon of the next. This creates the repeating sugar-phosphate chain that supports the sequence of bases.

DNA polymerase forms these bonds during replication by adding an incoming nucleotide to the growing strand. The nucleotide arrives as a triphosphate, and breaking high-energy phosphate linkages helps drive the reaction. DNA ligase can later seal phosphodiester bonds where replication leaves a nick, such as between adjacent Okazaki fragments on the lagging strand.

The alternatives describe different interactions. Peptide bonds join amino acids in proteins, not DNA nucleotides. Hydrogen bonds pair complementary bases across the two strands, while ionic interactions help DNA associate with positively charged proteins and metal ions. The phosphodiester backbone also gives DNA its overall negative charge.