in the dna structure, what kind of bonds hold the base pairs together?

Base pairs in DNA are held together by hydrogen bonds between complementary bases: adenine pairs with thymine (A–T) via two hydrogen bonds, and guanine pairs with cytosine (G–C) via three hydrogen bonds. These hydrogen bonds glue the two strands together in the double helix, while the backbone is linked by covalent bonds along each strand. The combination of hydrogen bonding for specificity and covalent backbone bonds provides both the stability and the accurate pairing needed for DNA replication and transcription.