There are three bonds between the cytosine and guanine molecules, as seen on the Education Portal. Cytosine and guanine are both nucleotide molecules. These two nucleotides form a strong hydrogen bond found in both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Clackamas Community College explains that two types of hydrogen bonds exist between DNA strands: adenine bonds with thymine (A-T) and cytosine bonds with guanine (C-G). RNA differs from DNA because RNA uses the uracil molecule instead of thymine (A-U). Adenine connects to thymine with two hydrogen bonds in DNA, and adenine connects to uracil with two bonds in RNA.
Three hydrogen bonds create a stronger connection than two hydrogen bonds because number of hydrogen bonds directly effects the strength of the bond. This makes the cytosine-guanine bond stronger than the adenine-thymine bond in DNA (and the adenine-uracil bond in RNA) because the cytosine-guanine connection has one more hydrogen bond.
All three bonds between cytosine and guanine contain hydrogen on either the cytosine or the guanine molecule. Cytosine connects one of its hydrogen atoms to an oxygen molecule on guanine forming one connection. The next bond connects the nitrogen atom to the hydrogen atom on the guanine molecule. The third bond connects the oxygen atom to another hydrogen atom on the guanine molecule.