The base pairs in a DNA strand are held together with hydrogen bonds. In what way would a cell be most affected if these were covalent bonds instead? The cell would need to make new DNA each time the strand was opened. The cell would only be able to open and close the DNA strand when it replicated. The cell would have to take in and use more energy in order to break the covalent bonds. The cell would need to replace the nitrogenous bases each time the DNA strand opened.