We have this stem section here in which the DNA molecules essentially intertwine along a common axis. And this is the same type of structure that we see in the DNA molecules. So we have these two complementary strands. The problem here is these strands actually consist of a single strand and in DNA molecules we have two different strands. So in RNA molecules because they exist predominantly as a single strand these complementary sequences here and here. So the blue and the red come from that same polynucleotide chain.