So the direction of the movement of the fork of replication is the same as the direction of the movement of our helicase enzyme. So as the helicase moves this way, the fork of replication also moves along with it. Now, as our doublestranded DNA molecule unwinds, it causes the DNA to super coil. And these super coils are known as positive super coils. And these positive super coils basically increase the stress, increase the energy of our double stranded DNA molecule. And this makes it very difficult for the helicase to actually continually unwind that double stranded DNA molecule.