In this video, we're going to talk more details about step 1a in the steps of DNA cloning, which is using restriction enzymes. Recall that restriction enzymes are enzymes themselves that are specifically important for cleaving or cutting the DNA at specific locations called restriction sites on the DNA, and that is going to produce sticky ends. We are going to define restriction sites and sticky ends down below in our text. Restriction sites are really just defined as specific sequences of DNA where a restriction enzyme will bind and cut the DNA. These restriction enzymes do not just bind and cut to any region of the DNA. They only bind to very specific regions of the DNA and only cut very specific sequences, producing sticky ends. Sticky ends are really just a single-stranded DNA overhang that is produced from the restriction digestion reaction.
We can get a better feel for this down below in our image, looking at restriction enzymes, restriction sites, and sticky ends. Notice over here on the left-hand side, what we have is a specific DNA molecule. This DNA molecule has a specific region called the restriction site, and this specific region is going to have a specific DNA sequence that is going to be recognized by the restriction enzyme. The restriction enzyme is symbolized here in this image as a little pair of scissors even though it is a complex enzyme that is going to be binding to the restriction site and cutting it. When these restriction enzymes cut at the restriction site, they usually generate these sticky ends, creating a staggered type of cut in the DNA. Notice that the DNA is being cut in this kind of staggered way. When it's cut in this staggered way, it creates overhangs, these single-stranded DNA overhangs that are kind of sticking out of the rest of the molecule. These are the sticky ends that we are referring to. The reason they're called sticky ends is because they can still complementarily base pair to other matching sticky ends as we'll talk about moving forward in our course.
But for now, this here concludes our brief lesson on step 1a, using restriction enzymes, and how restriction enzymes will bind and cut restriction sites to generate sticky ends and separate molecules. We'll be able to get some practice applying these concepts and talk more about step 1b as we move forward. So, I'll see you in our next video.
