In this video, we're going to introduce replication forks. Recall from our last lesson video that DNA replication begins at a specific set of DNA sequences called the origin of replication or just the ori for short. It turns out that many different proteins are going to bind to this origin of replication and those proteins are going to separate the 2 strands of DNA, unwinding the DNA so that DNA replication can begin. This unwinding forms a replication fork, which is sometimes also referred to as a replication bubble. Replication forks are really just these Y-shaped regions that are at the end of the bubble where DNA is unwound.

We'll be able to see the replication forks down below here in our image. If we take a look at this image, what you'll notice is that over on this side, we're showing you this replication fork. You can see that the DNA strands have unwound, so we have the old original DNA strand, which is a darker blue color, and you'll see that they're starting to be separated here. There's a separation of these two strands. The separation of these two strands creates the replication forks, or the replication bubbles.

You'll notice that at each of these positions on each side of this unwinding is a replication fork. The replication forks are indicated with these yellow backgrounds that you see here and over here, and you'll notice the Y-shaped regions at the end of the bubble where DNA is unwound. You'll notice that it does kind of create somewhat of a bubble. From here to here there's a little bit of a bubble and sometimes it's referred to as the replication bubble.

What you'll notice here is that DNA replication is actually going to proceed bidirectionally. Bidirectionally just means that it's going to occur in both directions, at each replication fork. You'll see that the direction of DNA replication, and the replication fork is going to be indicated by these red arrows. DNA replication is going to proceed in this direction at this replication fork and it will also proceed in this direction for this replication fork as well. That's important to keep in mind moving forward because we're going to talk about DNA replication at just one replication fork, but we have to keep in mind that DNA replication occurs at the other replication fork in the opposite direction.

DNA replication proceeds bidirectionally in both directions at each replication fork. Once again, we're going to talk more about the process of DNA replication, involving these RNA primers and these different strands as we move forward in our course. But for now, this here concludes our video introducing the terms replication forks, and we'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.