12. Which type of chemical
bond maintains the pairing of
each chain in the DNA
molecule?

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!
To form the DNA molecule, purine bases
bind to bases by
intermolecular called hydrogen
bonds. bonds occur when
there is hydrogen near one of these
electronegative elements: flu,
o or .

In such conditions hydrogen looks like
having lost for those elements
and a very strong polarization is
created. The highly hydrogen
attracts pairs of electrons of other
molecules making a hydrogen .