But in eucalyak acid, these bonds are phosphodia estate bonds and we'll see exactly what these bonds look like in a future lecture. So if we examine, for example, a DNA molecule this is what the DNA molecule actually looks like for DNA. Because of the structure of the sugar and DNA the DNA molecule is able to form a double helix formation. And what the double helix means is we have two individual strands of DNA that run antiparallel with respect to one another. Now, what allows them to actually form this antiparall arrangement is the fact that the bases are complementary with respect to one another. So to see what we mean, let's take a look at the following diagram.