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. So this here is our sugar. The blue section is the phosphate group and the green section is our nitrogenous base. And this three molecule component is known as a monomer, a nucleotide.