Hydrogen Bonding

Because hydrogen bonding is such a dominating force in secondary structure, we will take a little closer look. Water is a simple example of hydrogen bonding, but the double helix of DNA is also held together primarily by hydrogen bonding. The bases on the inside of the DNA molecule hydrogen bond to each other and cause the primary sequence of bases to twist and form a double helix.

Below are chemical representations of the four bases that are found in DNA. The dashed lines represent the hydrogen bonds that hold the double helix together. Adenine and thymine pair up and cytosine and guanine pair up to give DNA its complex structure.

Below are two models of the base pair hydrogen bonding in DNA. On the left is the adenine/thymine pair and on the right is the cytosine/guanine pair.

Hold the arrow from your mouse over the base pairs and hold down the left mouse button. This will allow you to move and manipulate the structures.

Things To Think About