1. Hydrogen bond
2. Nonpolar covalent bond
3. Ionic bond
4. Polar covalent bond
5. Sugar-phosphate bond
2. Nonpolar covalent bond
3. Ionic bond
4. Polar covalent bond
5. Sugar-phosphate bond
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hydrogen bond. The complementing DNA strands of the double helix are kept attached by the hyrdogen bonding of the nucleic acids. The bonding occurs betwee guanine and cytosine as well as adenine and thymine.